Bill Cipher

"Alright, listen up, you one-lifespan, three-dimensional, five-sense skin puppets! For one trillion years I've been trapped in my own decaying dimension, waiting for a new universe to call my own. Name's Bill! But you can call me your new lord and master for all of eternity!"

- Bill Cipher to Gravity Falls as Weirdmageddon begins

Bill Cipher is the main antagonist of the Disney XD series, Gravity Falls, although he doesn't play a central role in the series until the season 1 finale. He is a very powerful dream demon who means to bring about the end of the world by opening a rift between his Nightmare Realm and the real world. He has mysterious motives and a vendetta against the Pines Family, specifically Stanford.

He was voiced by the series' creator, Alex Hirsch.

Appearance
Bill appears as a floating, yellow triangle with a single cartoon eye in the center (though sometimes near the upper corner), a black bowtie and top hat, and thin black limbs. He is sometimes seen holding a yellow or black cane as well. Bill's body also flashes when he speaks, as he has no mouth. When angered however, his color is inverted, with his eye turning black, outline turning white and yellow turning a glowing red, although his form can change to that which is desired at will. A tapestry hanging from the wall in Northwest Mansion Mystery depicts him as black or ash grey instead of yellow and with a red eye. In The Last Mabelcorn he appears for a few moments as black with a yellow eye.

In the three-part series finale, Weirdmageddon, Bill assumes multiple three-dimensional forms, including a black multi-tiered and multi-armed pyramid, a three-dimensional version of his default yellow form (including a giant version), and his most horrifying and terrible form of all, that of a colossal red multi-tiered pyramid with 8 different glowing limbs resembling a spider, sharp teeth and tongues erupting from his body, and a black eye with a lizard-like yellow pupil, which he assumes during the final battle as he hunts down Dipper and Mabel Pines.

As he is being erased and speaking his hidden resurrection spell, he shape-shifts into several different forms in an attempt to escape, including his angry red form, a stone like form with two stone pyramids which could rotate with one eye one each side which could rotate and a stone block having his arms and bowtie, a distorted form with several green eyes and limbs, flashing between yellow, light red, blue, and orange, before finally assuming his black form with a red eye as seen on the tapestry. When Stanley punches him, he briefly flashes back to his default yellow form before being wiped out completely.

While possessing a person, that person's body will take on a pale tone to their skin, and their eyes will appear yellow with black slits, similar to his own.

If needed, Bill's yellow main portion or his eye can show images like a screen.

Personality
Bill at first seems to be affable and polite, albeit obnoxious, and slightly sadistic, but this easily changes within minutes of his debut, especially when he reveals his true nature: that of a highly intelligent, manipulative, murderous, and evil psychopath. He usually speaks with a high-pitched voice with a synthetized effect, but when furious or expressive, it becomes deep, guttural and satanic, similar to traditional demon depictions.

Bill seems to display symptoms of antisocial personality disorder. Symptoms include lying, feeling no remorse, and showing hostility and sadism.

He also enjoys hurting himself, as he tortures Dipper's body while possessing it, and has no problem killing or hurting children like Dipper and Mabel. An expert manipulator and master liar, he is clearly capable of fooling others into trusting him long enough for him to betray them in a heartbeat, and is falsely affable enough to influence others into playing pawns or making deals with him (which he will almost always double cross to his advantage). However, while an easily angered madman he is also highly intelligent and decisive, knowing when to pull out of a fight. As of The Last Mabelcorn, Bill is shown to be far more than simply a sadistic psychopath; he is calculating, malevolent, and diabolical, easily becoming one of the most fearsome and powerful Disney villains thus far.

Bill is also known for his complete disregard of rules and morals, as he considers laws and physics to be quite senseless and doesn't even care about the consequences of his actions that can endanger the fabric of existence, as he considers the idea of destroying the Earth as a mere game to him. He dedicated his own existence of spreading complete chaos and his selfish philosophy of doing whatever he wants without care for consequences.

However, in his final moments, Bill is shown to be absolutely terrified of dying as seen when being exploited by his own weakness, when he is trapped into Stanley's mind he attempts to goad Stan to let him out, only for Stan to punch him out and erase him from existence for good.

Before Gravity Falls
In the episode Weirdmageddon: Part I, Bill reveals he has been trapped in a decaying dimension, "waiting for a new universe" to call his own, for 1 trillion years. Ford Pines, Bill's main enemy, stated in an earlier episode that he's older than the Milky Way (which is 13.2 billion years old). Assuming that he's old enough to have recalled 1 trillion years of mental torment, this would mean he's older than our dimension by at least 987 billion years. In that same episode, he also referred to the populace of Gravity Falls as "single lifespanned", meaning he may have had numerous lifespans, and he may have either lived through those 1 trillion years in different lifespans, or he may have had lifespans before his time in the dimension. Other than his possible age, his "early life" (if whatever he is even has a definitive "life"), is completely unknown.

Before his debut in the episode Dreamscaperers, Bill Cipher made a cameo in the background of numerous episodes as drawings on the walls, card backings, and even in a single frame of the opening sequence, and being alluded to by series creator Alex Hirsch for the length of the season, before finally debuting in the penultimate episode.

Season 1
In that episode, the first season's main antagonist, Li'l Gideon, summoned him using a ritual found in Journal #2 to have him steal the combination to Stan Pines' safe via invading his mind. Bill made a deal with Gideon, saying that if he found the memory containing the combination, Gideon would help him with his plans, probably by Bill possessing his body. Later on, after the protagonists found their own way into Stan’s mind with Journal #3, they met Bill where he warned them to keep out of it, and showed his strength by blasting a hole in Dipper’s chest, sending Mabel a few seconds into the future, and blinking two characters she was thinking about into existence before flying into the shack in Stan’s mind. The trio followed him to try and find the memory before he could, and when they did Soos offered to destroy it with his strength, but revealed he was actually Bill in disguise, who took the memory to read it to Gideon.

However, Mabel and Soos caught up with him while Dipper looked for a personal memory, being able to knock the memory into the Bottomless Pit from the episode of the same name through one of Stan’s other memories. Seeing this, Gideon called off the deal and switched to “Plan B”, which enraged Bill to the point of growing into his ‘angry form’ and surrounding the room in flames, cornering the protagonists atop a giant stone Stan, where he tortured them by making them experience their worst nightmares. After killing Mabel’s two dream characters and threatening to do the same to Mabel and Soos, Dipper arrived just in time, having been taught by Stan in the personal memory that they can do whatever they can think in the Mindscape. They then used this to fight and overpower Bill.

Before they could defeat him though, Bill teleported them all to a blank white space, proving he was still far more powerful. But instead of killing them he stated he was impressed by them, letting them live since they might be useful later. He gave them a warning that a darkness was approaching and that everything they cared about would change. He promptly teleported away, saying he’d be watching them until then.

Season 2
Bill later returned in the Season 2 episode Sock Opera, where he offered to help Dipper find the password to The Author’s laptop in return for a ‘favor’. Dipper denied his offer and Bill disappeared, telling him he’d be back when he was ready to change his mind. He later reappeared when Dipper failed too many times to guess the password, forcing the computer to erase all its data after a countdown. During the countdown, Bill reappeared, stating Dipper looked desperate and reprised his offer, taking advantage of Dipper’s desperation and telling him that he only wanted a puppet. Dipper tried to resist, saying the puppets were for Mabel’s sock puppet play, but Bill was able to convince him by asking him what she had done for him lately, reminding Dipper of how much he’s sacrificed for her without her doing anything in return.

Dipper finally agreed to the deal, only for Bill to remove his soul from his body and possess it, making Dipper the ‘puppet’. He then smashed the laptop and proceeded to express his joy and ‘test’ his new body by slapping it in the face. Upon being asked why he had broken his word, Bill revealed that Dipper was getting too close to major secrets and that he didn’t need the boy getting in his way. He then left to destroy Journal #3 to stop him for good. After Mabel unknowingly told ‘Bipper’ she was using the journal as a prop in her play, he convinced her to let him play a part in it in order to get closer to the book. Dipper followed him there though and was able to tell Mabel what happened, and she went to get the book.

However she was confronted by Bipper, who threatened to drop Mabel from the catwalk and ruin her play if she didn’t hand over the journal. Mabel almost gives him the journal and he asks her who would sacrifice everything they’ve worked towards for their sibling. Mabel responded by telling him Dipper sacrificed for her, and returns it by throwing the play. Mabel and Bipper had then fought onstage, with him easily overpowering her. However, she exploits Dippers body’s weaknesses, such as the fact that he hadn’t slept in more than 50 or so hours and is able to defeat him. With the body exhausted to the point of unconsciousness, Bill is thrown out of Dipper's body and Dipper takes it back. The twins share a moment, but Bill possesses one of the sock puppets, telling them they can’t stop him. Mabel sets off the fireworks used in her play, destroying the puppet and forcing him once more into retreat.

Bill appeared a third time for a short cameo at the end of Northwest Mansion Mystery. After, Old Man McGucket fixed the laptop and warned Dipper that the end of the world was coming and that they had to stop it, as the screen panned off to a tapestry with a black and red Bill on it gazing over a burning landscape, alluding that Bill was what was to cause the apocalypse.

While not specifically present, Bill was clearly referenced numerous times in the episode A Tale of Two Stans, first when a younger McGucket spoke the ominous phrase "When Gravity Falls and earth becomes sky, beware the beast with just one eye", and again when Ford, Stan's brother, inspected his shape out of suspicion of him being possessed by Bill, notably by checking the give away eye shape with a flashlight.

He then made another direct, though off-screen appearance at the end of the episode "The Stanchurian Candidate", when Gideon attempted re-summoning him from his prison cell to strike another deal, possibly to destroy the pines family in exchange for a host to possess in Gideon.

Bill finally made his third appearance in the episode "The Last Mabelcorn", where he came to Ford in a dream, establishing their past relationship and warning Stanford that he was coming. In response, Stanford had Mabel retrieve Unicorn Hair in order to cast a spell that would protect the Mystery Shack from Bill Cipher. In the meantime, Stanford showed Dipper a machine that would scan their thoughts and shield their minds from the demon as a last resort in case Mabel failed. Curious of Ford's thoughts and his history with Bill, Dipper attached the machine to Ford in his sleep and saw that he was dreaming of Bill and Ford making a deal. In his horror, Dipper also knocked over the curtains on the walls, revealing the room to have once been a shrine to Bill as many paintings of him hang from the walls and statues of him stand in the corners. Because of this Dipper believes Ford to be possessed by Bill, or worse, in league with him, to the point of almost using the Memory Eraser on him. Ford proves he's still on their side though and reveals his history with Bill. Apparently, Stanford hit a roadblock in his research of Gravity Falls, but found writing in a cave depicting a being of knowledge that could help him, leading him to summon him.

Bill first appeared to Stanford in a dream, where he seemed to be affable and friendly, offering a game of chess and "Dream Tea". Bill lied to Ford, telling him he was a muse that chose a brilliant mind to inspire every century. In his flattery Ford made a deal with Bill, that in exchange for total access to Ford's mind Bill would help Ford by telling him to build the portal. But when McGucket was sucked into the portal, Bill's true plans were revealed and the triangle exposed as a malevolent, psychotic monster. It is learned he was going to use the portal to open a gateway between the Nightmare Realm he exists in and the physical world, allowing him to achieve physical form and unleash his fellow demons, in his own words "teach this dimension how to party". It is also revealed that Bill is older than "anything in our universe", and that Bill had been manipulating history by making deals with people throughout time, apparently for the sole purpose of one day creating the portal. Ford tells Dipper this is why they must protect the Dimensional Rift, and that if they worked together they could be the last people to be tricked by Bill. After the spell is successful, Ford tells Dipper that anyone inside the bubble surrounding the shack would be safe from Bill's influence. However, Bill is watching them from his dimension, and decides that if he can't affect anyone in the Mystery Shack, he would have to look for his next pawn on the outside as a series of images of the rest of the cast flash over his eye.

Bill next appeared in "Dipper and Mabel VS The Future", where he possessed Blendin Blandin in order to have a vessel to destroy the rift. Using Blendin, he convinced Mabel to steal the rift for him by promising her that he can extend summer for her with it for as long as she wanted. As it turns out, the rift is in Dipper's backpack (which Mabel took by accident). Upon receiving the rift from Mabel, Bill promptly smashes it on the ground, opening the gateway to the nightmare realm. Leaving Blendin's body, the episode ends with Bill laughing triumphantly at Ford and Dipper as he makes his entrance into the world and ignites "Weirdmageddon".

Weirdmageddon
In "Weirdmageddon - Part 1", Bill finally attains a physical form and frees his gang from his dimension. He then wreaks havoc on the town of Gravity Falls and turns it into an apocalyptic, nonsensical wasteland while declaring that he intends to do this to the entire universe. Dipper and Ford then enact a plan to take out Bill with a quantum destabilizer, but fail due to the abnormal environment. After being captured by Bill, Ford is offered the chance to join him, but is turned into a golden backscratcher by the demon after refusing. Dipper tries to stop Bill, but his lack of information of the dream demon causes him to be easily defeated. Bill "helps" Dipper by inflaming all three journals and sicks his henchmen, 8-Ball and Teeth, on the boy to eat him and flies up to his new, floating castle to party with his crew. After three days of non-stop partying, Bill is confronted by Time Baby and his police force, who came to arrest him for both using the body of Blendin Blandin for his scheme and to stop his plot to alter reality. Bill, however, is unfazed and promptly kills Time Baby and his police squad by disintegrating them, much to the shock of Blendin, who escapes away.

Meanwhile, Dipper, after escaping from 8-Ball and Teeth, is on the search for his sister, Mabel, who Bill imprisoned in order to honor his deal with Gideon (who he also broke out of jail). After a confrontation with Dipper and Wendy, Gideon calls upon Bill's minions to take them and Soos to the dungeon in Bill's castle. After being convinced by Dipper that Mabel will never love him and that he can't force her to, a newly reformed Gideon decides to help aid in his former enemy's cause by giving him the key to Mabel's imprisonment bubble. He and his prison goons then leave to confront Bill and his minions.

In "Weirdmageddon 2: Escape From Reality", Bill taps a fork on Golden Ford to grab the partying monsters' attention, and announces that they will now unleash their chaos on the whole world. As all other monsters take to the skies to spread destruction, they slam into an invisible forcefield without warning, Bill exclaiming, "WHAT?!" He figures out that their chaos has formed a barrier around Gravity Falls, the only area they can currently reside in, meaning that they can't spread their destruction throughout the world. Upon learning of this, Bill realizes that this might be more difficult that he thought. One monster complains that they broke something, and Bill angrily retorts, "WALK IT OFF!"

He considers getting Ford 'out of retirement', believing that the latter may have the answer to breaking down the barrier. He then finds out from Keyhole that Gideon let Dipper, Wendy, and Soos into Mabel's bubble. Bill simply laughs, explaining how the bubble is his most diabolical trap of all. He tells Keyhole to fetch Gideon and have the day off while Bill prepares to expand his world upon Earth, and later, the universe.

In "Weirdmageddon 3: Take Back the Falls", Bill releases Ford from his frozen prison to gain knowledge about the forcefield that's keeping him in Gravity Falls. Bill establishes that he comes from a flat dimension where he is implied to have committed mass genocide against his own kind, including his family hinted back in the 2015 Bill Cipher AMA on Reddit. Ford refuses to cooperate with him, which instantly tests Bill's patience. Bill starts torturing Ford in order to get the answer to his dilemma. As soon as the Pines family and their resistance group made a giant robot to fight their way to the Fearamid, Bill goes after the Pines and petrifies Ford before he could try to stop him. Bill orders his henchmaniacs to fight the resistance. When that fails, as the townspeople worked together to take down most of the henchmaniacs, Bill takes matters into his own hands and tries to destroy the robot, but with no success, due to the Mystery Shack being protected by unicorn hair that Dipper and Ford enforced back in The Last Mabelcorn. The robot tears out Bill's eye, where he complains to the resistance on how long it will take for it to regenerate. Unfortunately, as soon as Bill regenerates a new eye, he instantly finds the robot's weak spot and uses it to take down the robot easily.

The Pines family unites with some of the other townspeople in order to learn about Bill's weakness. They learn about the Bill Cipher Wheel and tried to use in order to defeat Bill for good, but it fails, as Stan refuses to hold hands with Ford due to bearing a grudge and holding some resentment for his twin brother over the whole portal incident. Bill immediately retaliates by transforming Soos, Wendy, McGucket, Pacifica, Robbie, and Gideon into tapestries in his lair. Dipper and Mabel risk their lives by angering Bill with their pranks in order to distract him, and he transforms into a horrifying multi-tiered being in his rage to hunt them down once and for all, while Stan and Ford try to figure an alternative solution.

Death
When Bill finally captures Dipper and Mabel and ponders on who to kill first, Ford reluctantly surrenders and orders Bill to let the twins and his brother go in exchange for access to his mind. Bill gladly accepts and instantly leaves his physical form to enter Ford's mind. However, it turns out Ford and Stan planned a switcheroo and Bill ends up in Stan's mind, where Stan taunts him for falling for the trick. Ford, with no other option, reluctantly uses the Blind Eye Society's mind-erasing weapon to wipe out the memories of his twin brother in order to defeat Bill for good. Realizing that he's been tricked, Bill angrily calls off the deal, but he gets locked within Stan's mind as the dreamscape and living room of the Mystery Shack burn in flames thanks to the mind-erasing weapon. Bill cowardly pleads for mercy by appealing to Stan's greedy nature with riches and power, but Stan angrily refuses and proclaims that Bill has harmed the Pines family too much to deserve any mercy. As Bill begins to glitch, he furiously cries out Stanley's name and rushes at him, but Stan retaliates by punching Bill directly in the eye, obliterating the screaming dream demon and shattering him to pieces right before Stan's memories are completely wiped out.

With Bill seemingly erased from existence, Weirdmageddon has ended, all of the monsters were returned to their dimension, and the rift is finally sealed off for good, turning all of Gravity Falls back to the way before Weirdmageddon has started. As Stan manages to regain his memories (thanks to the help from the Pines family), the only apparent trace of Bill left is his physical form now turned into stone following his death. Bill's statue is later seen at the end of the episode, as well as the end of the episode's credits where it appears in real life, heavily implying that he still exists somewhere in the world and may someday return.

​Quotes
"Oh, oh, Gravity Falls, it is good to be back! Name's Bill Cipher, and I take it you're some kind of living ventriloquist dummy? [laughs] Just kidding, I know who you are, Gideon!"

- Bill Cipher after he is summoned

"Oh, I know lots of things! Lots of things..."

- Bill Cipher

"A darkness approaches. A day will come in the future where everything you care about will change... Until then I'll be watching you! I'll be watching you..."

- Bill Cipher foreshadowing Weirdmageddon

"Remember; reality is an illusion, the universe is a hologram, buy gold, bye!"

- Bill Cipher's most famous quote

"Ah, Stan's family, we meet at last! Question Mark, Shooting Star, Pine Tree, I had a hunch I might bump into you!"

- Bill Cipher meets Dipper, Mabel and Soos

"You're out of your league, kids. Turn around now before you see something you might regret."

- Bill Cipher "Boy, you kids sure are gullible! I knew you'd lead me straight to the code!"

- Bill Cipher

"YOU! You can't even imagine what you just cost me! Do you have any idea what I'm like WHEN I'M MAD??!!"

- Bill Cipher's Villainous Breakdown

"Hmm, let's see. Eenie meanie miney... YOU."

- Bill Cipher takes Dipper's body

"Pain is hilarious! And two eyes? This thing's deluxe!"

- Bill Cipher in Dipper's body

"But how can you stop me... if you don't exist? AHAHAHAHAHAHA!!!"

- Bill Cipher to Dipper

"It's funny how dumb you are!"

- Bill Cipher

"Well well well! You're awfully persistent, Pine Tree! Hats off to you!"

- Bill Cipher to Dipper

"Did you miss me? Admit it, you missed me!"

- Bill Cipher

"Ho ho-looks like Mr. Brainiac finally got smart! Let's just say that when that portal finishes charging up, your dimension is gonna learn how to PARTY! Right, guys?!"

- Bill revealing his true colors to Ford.

"At last! At long, long last! The gate between worlds has opened! The event one billion years prophesied has come to pass! The day has come! THE WORLD IS FINALLY MINE!"

- Bill Cipher "It's time we do a little redecorating-I could really use a castle of some kind! And how about some bubbles of pure madness?!? This party never stops! Time is dead and meaning has no meaning! Existence is upside down and I reign supreme! Welcome, one and all, to Weirdmageddon!"

- Bill Cipher brings forth Weirdmageddon

"We'll meet again. Don't know where. Don't when. Oh, I know we'll meet again, some sunny day."

- Bill Cipher singing

"As you may have noticed, I've recently had a multi-dimensional makeover! I control space, matter, and now that that dumb Baby's out of the way, time itself! But I wasn't always this way. You think those chains are tight? Imagine living in the second dimension. Flat minds in a flat world with flat dreams! I liberated my dimension, Stanford, and I'm here to liberate yours. There's just one hitch. As it turns out, my weirdness can't escape the magical confines of this town-there's something keeping me in!"

- Bill Cipher explaining himself to Stanford

"Listen Ford, if you just tell me that equation, finally your dimension will be free! Anything will be possible! I'll remake a fun world! A better world! A party that never ends with a host that never dies! No more restrictions! No more laws! You'd be one of us! All-powerful! Greater than anything you've imagined, and all I need is your help!"

- Bill Cipher to Ford

"You're making this so much harder than it needs to be! Everyone has a weakness, tough guy! I'll make you talk! It's only a matter of TIME!"

- Bill Cipher about to torture Ford

"So the mortals are trying to fight back, huh. Adorable!"

- Bill Cipher

"You're making a mistake!! I'll give you anything: money, fame, riches, infinite power, your own galaxy, PLEASE! (starts to glitch) NO!! What's HAPPENING TO ME?!!! (reversed) AXOLOTL, MY TIME HAS COME TO BURN, I INVOKE THE ANCIENT POWER THAT I MAY RETURN! (normally) STANLEY!!!!!"

- Bill's last words before being destroyed by Stanley.

Trivia

 * His full name is likely a reference to the Beale ciphers; encrypted manuscripts which are said to lead to a great, hidden treasure and which only one of three have been decoded.
 * This is entirely possible as codes and ciphers are hidden all throughout the series.
 * Bill can be summoned if one were to recite an incantation found in Journal 2.
 * He is based on The Eye of Providence, as creator Alex Hirsh confirmed in the Special "Behind the Pines" stating: "What if I took the triangle off the back of the dollar bill, dress him up in a top hat, and stupid little arms and legs, and named him Bill after the dollar?"
 * Bill Cipher has a strong resemblance with Dimentio from Super Paper Mario as:
 * Both have the main goal to destroy all life; though Dimentio actually wanted to destroy all the worlds to create "perfect" new ones for him to rule while Bill desired to merge his Nightmare Realm with the universe and create a new Weirdmageddon.
 * Both are always floating most of the time when they appear.
 * Both appear to have unlimited power, being considered the most powerful villains in their respective franchises.
 * Both made a deal with the protagonists to presumably give "help" to them when they most needed it and ended betraying them (Bill taking control over Dipper's body and Dimentio brainwashing Mario and Luigi to help him on his plans).
 * Both have humorous qualities, though being very ruthless on their goals and even when they are committing misdeeds.
 * Both help the main antagonists at first, but are later revealed to be the true main villains.
 * Various things were discovered about Bill Cipher during a Reddit AMA, including the possibility of him once having a family, having something to do with Gompers in the past, and his favorite music being 10 hours of Rising Shepard Tone.
 * The AMA also revealed that Bill Cipher thinks in capital letters.
 * It is never made clear what Bill truly is. While he is called a "demon" by other characters, creator Alex Hirsch has confirmed that this is just a name for lack of better description. Ford even states that no one knows really what he is. Because of his reality warping abilities and bizarre nature, it is likely that he is inspired by the Outer Gods of Lovecraftian lore.
 * In addition to being inspired by Lovecraftian Lore, Bill Cipher is very similar to the Lovecraftian character, Yog-Sothoth. This is because both of them are Omniscient and All-Seeing.
 * Bill may not remain deceased for long. As he is about to be erased, he speaks an incantation that, when reversed, says "A-X-O-L-O-T-L, MY TIME HAS COME TO BURN, I INVOKE THE ANCIENT POWER THAT I MAY RETURN!" which heavily implies he'd casted a spell that would one day resurrect him, meaning he had one final and desperate backup plan to use during his demise, though this isn't confirmed.
 * The real-life Bill statue could be an interpretation of Bill dying in the world of Gravity Falls, but regenerating in our own world, meaning that he will indeed return and that his spell proved successful, however there is no confirmation of this.
 * There is also the probability that Bill is slowly regenerating from being punched to pieces within Stanley's mind, which would explain how much simpler it was for Stan to regain his memory.
 * Bill Cipher share some similarities toward Discord from My Little Pony: Friendship is Magic.
 * Both have odd appearances.
 * Both create a world of neverending chaos for fun.
 * Both can alter reality and possess nearly limitless power.
 * Both have comedic traits.
 * Both first start their chaos in the first location they seek (Ponyville for Discord and Gravity Falls for Bill Cipher).
 * Both are tricksters.
 * Both wanted to take away the main items that will be the key to defeat them (Elements of Harmony for Discord and the 3 Journal for Bill Cipher)
 * Both act friendly toward a protagonist and trick them to reach their goals (Fluttershy for Discord and Stanford Pines for Bill Cipher)
 * Both are immortal.
 * Both come from a alternate dimension (Chaosville for Discord and the 2nd Dimension for Bill Cipher).
 * Although there is a major difference: while Discord was reformed, Bill was not.