Zombozo

Zombozo is one of Ben's first enemies.

A cruel and creepy clown mastermind with some similarities to the Joker from Batman, Zombozo was mostly hard to defeat by Ben because he was afraid of clowns and him. Ben managed to conquer this fear and defeat Zombozo.

Despite being a minor villain in the original show, Zombozo played a key role by introducing the Circus Freak Trio, who later became recurring villains. His episode was also the first one to hint the existence of Ghostfreak's true form, possibly anticipating the Zs'Skayr storyline.

Personality
Zombozo is portrayed as a grim and cruel clown with a dark sense of humor. In his original appearance, this was shown by him enjoying making dark jokes about his enemies and his feeding, even when acting (i.e.: "Laughter truly is the best medicine...for me!"), and cruelly taking pleasure to use Ben's fear of clowns against him. In Ultimate Alien, he displayed much more sadistic and psychopathic behavior, using lethal weapons, trying to make Ben and his family suffer by killing Sandra, slowly and scarily. It was even suggested at the beginning of his comeback he had buried someone. So far, he's the only known person that Charmcaster fears besides her uncle Hex.

Zombozo never or rarely attacks alone, always gathering together a crew to do his dirty work for him. Originally, this was his Circus Freak Trio and later Zombozo leads a coallition between Vulkanus, Charmcaster and Sevenseven (and eight others who were all warded off by Max before he was injured fending off Sevenseven).

Powers and Abilities
In his original appearance, Zombozo was using a machine called the "Psyclown" to give him the ability to drain happiness from people when they're laughing. This left them depleted, weakened and sad. In the most extreme case, it even seemed to age people, as it did with Gwen. The machine was connected to him by a line, giving him the ability to fly.

Zombozo is able to teleport in an explosion of smoke and confetti.

Zombozo could terrorize Ben with frightening images, he was merely creating illusions. Since he didn't do this in Ultimate Alien, it's possible there were possible with the Psyclown.

In Ultimate Alien, Zombozo relies on various clown-based gadgets as weapon, including caltrops, an acid seltzer bottle, steel streamers, an extending arm, an electric joy buzzer, dynamite, and an over-sized mallet.

In Cosmic Destruction, it also shows Zombozo being able to fly by holding on to a flying toy airplane.

Original Series
In his first appearance, Zombozo stages shows to bring people in and then uses a machine, he calls the "Psyclown", to drain the happiness and life energy from them for him to "eat", leaving them depleted and sad. In the most extreme cases, it even seems to age people. During all this, his the Circus Freak Trio rob the town.

Though not notably powerful amongst Ben's enemies, he proved to be somewhat hard to defeat, as Ben was suffering of coulrophobia (fear of clowns) at the time and so he couldn't fight him properly. Zombozo was eventually defeated when Ben overcame his fear of clowns after seeing the effect of the Psyclown on Max and Gwen, and Ghostfreak terrorized Zombozo by peeling back his skin, causing him to 'explode' in a burst of confetti (he only escaped) (At this point Ben implies that Zs'Skayr may have taken over by saying "Whoa! That kinda even freaked me out."). It is unknown where Zombozo went.

While Zombozo's henchmen reappeared in later episodes, he himself did not in the rest of the episodes in the original series. The three claimed that they have not seen Zombozo since his defeat.

Ben 10: Ultimate Alien
After his long absence, Zombozo eventually returned in Hit 'Em Where They Live. After Ben's identity was revealed to the world, he, as their "ringmaster", organized attacks against Ben's family with the help of several of Ben's enemies (including Sevenseven, Charmcaster, Vulkanus and eight unidentified villains) in an attempt to get revenge on Ben. After most of the attacks were stopped by Max, Zombozo formed a team with Charmcaster and Vulkanus. He also appeared to have buried someone or something, due to him coming in with a shovel.

Zombozo kidnapped Sandra and used her as a hostage to bring Ben, Gwen and Kevin to his hideout, then separate them and let Charmcaster and Vulkanus take them down one on one. His plan eventually backfired when he tried to murder Sandra in a slow and cruel way, as it caused Gwen to get angry and transform into her Anodite form, growing to giant size and shouting at him to leave the Tennyson family and Kevin's family alone and to spread the word to all of the other villains.

According to Dwayne, Gwen had let Zombozo go to warn the other villains of her warning message. It is unknown if he did or where he went.

Ben 10: Omniverse
Zombozo has been confirmed to return in Ben 10: Omniverse. He was shown in the sneak peek being chased by Ben's Team and he was holding a jar with a brain inside it.

Ben 10 Ultimate Alien: Cosmic Destruction
Zombozo appears in Cosmic Destruction in Tokyo. He does not say why he is there, nor does Ben ask why.

However, Ben does tell him to give him Cooper's location, which Zombozo denies. He then attempts to kill Ben twice, though both attempts fail pathetically, it forces Ben to defeat Zombozo as Ultimate Spidermonkey. After defeat, Zombozo laughs hysterically, which only results in Ultimate Spidermonkey throwing him into a web he made. Ben then says, "Am I good? Or am I good?"

Ben 10

 * The Last Laugh (first appearance)

Ben 10: Ultimate Alien

 * Hit 'Em Where They Live (first re-appearance)

Video Games

 * Ben 10 Ultimate Alien: Cosmic Destruction

Trivia

 * Zombozo was voiced by John Kassir (of the Crypt Keeper/Tales from the Crypt fame) in the original series, and by John DiMaggio (the voice actor for Bender and Teen Titans villain Brother Blood) in Ultimate Alien.
 * Ben supposedly didn't remember fighting Zombozo in the original series; according to Dwayne, Ben pretended he didn't remember because he didn't want to admit to Kevin he used to be afraid of clowns.
 * Both of Zombozo's appearances end with him being scared off by one of the main characters in an alien form.
 * Zombozo's name might be an amalgam on the words Zombie and Bozo (a famous clown).
 * In Ultimate Alien, Zombozo's weapons, gadgets, and laugh resemble those used by Batman's archenemy, The Joker (electric joy buzzer and giant mallet are Joker mainstays) while his attempts to terrorize Ben into submission in the original series is closer to another famed Batman villain, Scarecrow.
 * In Ultimate Alien, it seems Gwen holds a grudge against Zombozo due to the fact that he almost sucked her dry of happiness.
 * When asked if Zombozo will return, Dwayne answered "not if he knows what's good for him". However, he was confirmed to return in Ben 10: Omniverse.