King Boo

"But I am a KING among Boos! I swear it, I shall fear no mere house-cleaning device!"

- King Boo

King Boo is a recurring villain in the Mario games, who appears under different shapes and roles. He is the king of Boos as his name suggests. He is a disturbing individual who has a particular contempt for scaring. Despite having the same name and role, the King Boo from the main games seems different from the character in the Luigi's Mansion spin-off.

Super Mario Sunshine
A Boo with the same name as King Boo appears in Super Mario Sunshine, where he fought Mario at the casino of Sirena Beach in Super Mario Sunshine. He uses a slot machine in battle, and Mario defeats him by throwing spicy peppers at his tongue, setting it on fire, and then throwing fruits at him. After three hits, King Boo is destroyed.

Contrary to popular belief, this Boo is NOT the King Boo fans are familiar and several evidence are given: its name in the Japanese name translates as "Boss Boo" (which King Boo himself has never been called); its crude appearance and death by dissolving into goop suggests it's actually a painting made by Jr.'s Magic Paintbrush; lastly, Sunshine (in a rather rare case where Mario games have confirmed chronologically) takes place after the events of the first Luigi's Mansion, which explains Luigi's absence.

Super Mario 64 DS
King Boo also makes an appearance as a boss character in the DS remake of Super Mario 64. King Boo aids Bowser with taking over Peach's castle. He also managed to kidnap Luigi. Mario had to venture into Big Boo's Haunt and locate a picture of Luigi. Once he found and entered the picture, Mario finds himself in a world where King Boo is. He taunts Mario thinking that he'll never find his brother. However, by listening to King Boo's laughter, Mario was able to locate to where King Boo was hiding. When he entered the room where King Boo was hiding, Mario spots a large mirror. Eventually, King Boo arrived and confronted Mario. Mario had to use the mirror to locate King Boo, and stomp on King Boo several times. Eventually, Mario managed to defeat King Boo, and rescue Luigi.

Super Princess Peach
However, he is revived by Bowser at least once more, and appears as the third boss in Super Princess Peach, at Shriek Mansion. He is shown to have a weakness for extremely bright lights, as when Peach uses Rage to light all the torches in the room, King Boo takes damage. Once this happens five times, King Boo is destroyed.

Mario Kart series
He also appears in spinoffs such as Mario Kart: Double Dash!, in which he is an unlockable and playable character. He also appears as playable character in other Mario Kart games including; Mario Kart Wii. He also appears as a boss character in Mario Kart DS, and makes a cameo in Mario Kart Arcade GP 2.

Mario Baseball Series
King boo also appears as an enemy/playable character in the Mario Baseball series.

Mario Superstar Baseball
King Boo is a playable character in Mario Superstar Baseball and a member of Wario's baseball team called the Wario Greats. He does not need to be unlocked. He is a power hitter, using his white, crowned, Boo-like baseball bat to hit long outfield drives and even homeruns. King Boo has chemistry with Boo and Petey Piranha, and he has bad chemistry with Luigi. However, like Boo, his hits are usually very curved, and this causes them to be fouls most of the time.

Mario Super Sluggers
King Boo reappears in Mario Super Sluggers and he is one of the few characters that were on Wario's team in the last game that are still on it. He is once again a power hitter, and he also excels in pitching, with both stats being his highest. In Challenge Mode, he appears immediately after the player defeats Bowser Jr. at the Wario City stadium, stating that he turned invisible and was watching the whole game. However, he is uninterested in joining the player's team unless the team has some Boos with them. This is accomplished by finding both Boo and the Mini Boos item. In this game, King Boo has chemistry with Petey Piranha, Boo, King K. Rool, and Wiggler, but he has bad chemistry with Mario, Luigi, Baby Mario, and Baby Luigi.

His baseball bat does not have a physical crown on it anymore. In this game, it is represented as a crown picture above the "Boo mouth" picture. As well, in this game only the colours of the jewels on his crown are reversed.

Mario Party Series
King Boo also made appearance in two Mario Party games. Both of which, appears as an enemy towards the players

Mario Party 8
King Boo makes his first appearance in a Mario Party game in Mario Party 8. He gives out Stars on his own course King Boo's Haunted Hideaway. He hides in one out of three altars and gives the player a Star for ten coins if they can find him where he is hiding. If the player is able to buy the Star, he will "summon the bizarre" and disappear, causing the player to jump into a Warp Pipe that returns them to the starting point. This "makeover mojo" causes the whole layout of the course to change. However, if they do not have enough coins, King Boo will cause a pitfall to appear under the player, causing them to return to the starting point and allowing the next player that reaches him to buy the Star. Additionally, if the player fails to steal anything from the board event Pickpocket Pinball, the hosting mouse sounds like King Boo. The player can purchase King Boo sounds from the Fun Bazaar, along with a figurine titled "King Boo's Revenge". When the player presses A Button on the figurine during the Figurine Parade, King Boo floats up and gives off a brilliant glow, as if he is a light bulb.

Mario Party 9
King Boo appears as the stage boss of the board Boo's Horror Castle in Mario Party 9. He is fought in the minigame, King Boo's Puzzle Attack, where the competitors line up power-ups in lines of three or more to deal damage to him. Once his health reaches halfway, he throws Boos onto the field which can stun the player's cursors, making them unable to move until they shake the Boo off. What is unique about his boss battle is that if a player gets the Final Attack, they get ten points instead of the usual three, likely because the players can easily accumulate points up to fifty. In the final fight against Bowser, King Boo can also appear to hinder the players' progress. If Bowser throws the die with all the stage bosses' faces on it and King Boo's face appears on top, King Boo will materialize above the stage. Then, he will summon five Boos that move in a counterclockwise direction while moving outwards. When the Boos reach the boundaries of the stage, King Boo summons another five Boos, except this time they move clockwise. After that, King Boo disappears from the battle unless his face appears on the top of the die again. King Boo also has a constellation that can be returned to the sky; it is called the Ghost Major. It is located in the farthest left portion of the sky, near Big Bob-omb's constellation and right next to Boo's constellation. Like all constellations, it can be bought for fifty Minigame Points.

Mario Party 10
King Boo reappears in Mario Party 10. He returns as a boss in the minigame King Boo's Tricky Tiles. In order to defeat him, the player must remember which platforms are false, and then run around until they can jump on a light switch (one is worth 3 points, and another worth 1 point). Like other bosses, King Boo will get angered after the players deplete his health halfway. The technique that King Boo uses is that he swaps Boos with platforms and he blocks the camera, so the player can't see the platforms very well and remember which ones are false. He can also be seen on the Luigi Board, which appears in the game's amiibo Party mode.

Mario & Sonic Olympic Games series
King Boo also made appearances in most of the Mario & Sonic Olympic Games series.

Mario & Sonic at the Olympic Winter Games
In the Wii version of Mario & Sonic at the Olympic Winter Games, King Boo appears as the first and sixth (in Individual Festival mode only) rival. King Boo races the player in the Alpine Skiing Downhill event in both Individual and Group Festival modes but he only races the player in Giant Slalom in the Individual Festival mode. King Boo has no skis so he goes down the hill smoothly. If the player loses to him, the guide (either Cream or Toad) says that it is unfair because King Boo has no skis.

In the Adventure Tours mode in the DS version, King Boo is the mid-boss of Polastraits. When the challenger approaches him, King Boo tells Mario/Sonic that he must race someone afraid of him. He selects Luigi and they must race in Giant Slalom. In this version, King Boo is transparent and the player can ski through him. He also appears slightly larger than in his other appearances.

Mario & Sonic at the London 2012 Olympic Games
King Boo appears in the next installment of the Mario & Sonic series, Mario and Sonic at the London 2012 Olympic Games. In the Wii version, he is one of the characters that can be found in the London Party mode, and when he is encountered, he will challenge the player to the Dream Sprint event. Since he has no feet, though, it is questionable how he gets the ball to roll. If the player reaches the goal line before him, they will get a sticker as an award.

In the 3DS version, King Boo teams up with a Boo to face Sonic and Tails in the Badminton Doubles event. After winning, the player completes Sonic's second episode.

Mario & Sonic at the Sochi 2014 Olympic Winter Games
King Boo appears in Mario & Sonic at the Sochi 2014 Olympic Winter Games as a rival in the Legends Showdown mode. He is found in Area 4, and is raced against in Short Track Speed Skating 1000m.

Mario Golf: World Tour
King Boo makes a cameo appearance in Mario Golf: World Tour on Hole 4 of Bowser's Castle. He is floating in the background alongside other Boos, and he is also much larger than in other games. His name can also appear on the tournament scoreboard.

Characteristics
Besides possessing the abilities of other Boos, including the ability to teleport, King Boo has a number of other magical powers. Notably, it should be mentioned that King Boo's power increases when he is in the presence of other Boos. King Boo also has the incredible power to materialize things out of thin air. He has also shown the ability to create Boos, bubbles, and blue fire, which he spits out of his mouth.

Although King Boo is a lot larger than regular Boos, he is not the largest of the Boos. However, even gigantic Boos like Boolossus follow his leadership, despite their superior size. This is likely because he is the most intelligent and the most powerful of the Boos. King Boo seems to have a passion for gambling, as the entrance to each wing in Luigi's Mansion was modeled after a playing card suit (spade, club, heart, and diamond), he is fought atop a slot machine in a casino in Super Mario Sunshine, and (though this is non-canon), his Rival match in Mario & Sonic at the London 2012 Olympics Games is at Bingo Highway, a casino-themed stage from Sonic Heroes.

King Boo has an extreme dislike for the Mario Bros., due to their constant intervention in the plans of the Boo leader and others of his kind, especially towards Luigi. He shows a bit of a snarky side in Dark Moon when he confronts Luigi with "Remember when you trapped me for all eternity in a painting? Good times." Lastly, King Boo has a distinct cackle, which is significantly lower in pitch than other Boos.

King Boo hates spicy things, as throwing a jalapeno pepper in his mouth will set his tongue on fire and make him vulnerable.

Trivia

 * King Boo's quote, "I don't plan to give up my favorite decoration. I like Mario where he is." is a quote derived from Star Wars VI: Return of the Jedi, when Jabba the Hutt said, "I don't plan to give up my favorite decoration. I like Captain Solo where he is."
 * Luigi is canonically the only Mario character to fight King Boo more than once, due to King Boo being his arch-enemy.
 * In the English version of Super Mario 64 DS, King Boo was mistranslated into Big Boo.
 * In the Mario Party 9 Sound Test, there are two voice sounds with the name "King Boo's Entrance"; one is King Boo and the other is actually Boo.
 * The Japanese, Dutch and Korean names for King Boo use the English word for king, instead of a word in their own dialects.
 * Although he commands a large band of Boos, not all Boos call King Boo their leader, with some Boos working directly for Bowser, and many others living peacefully with the other denizens of the Mushroom Kingdom, either independently or as part of a small band of Boos led by Lady Bow.