Uka Uka is Aku Aku's evil brother and a major antagonist in Super Smash Bros. Crossover. Uka Uka first appears in Season 21 after the heroes escape, causing Uka Uka to become angry at Dr. Neo Cortex, Dr. Eggman, Dr. Doom, Dr. Wily, and Zombie Reed since they were supposed to make the prison inescapable. Uka Uka overhears Yami Bakura tell Samus Aran not to go after the Infinity Sword and Infinity Gauntlet, which the heroes took from The Dark Surfer, and decides to let the heroes keep it since it will corrupt them. When this later comes true as Zombie Wasp becomes Dark Wasp, Uka Uka begins laughing evilly, telling Dark Wasp to wreak unholy havoc on the heroes. Later, when the heroes and villains team up to destroy Gigadark Bowser and free Samus, Uka Uka and the Razenoids help protect Gigadark Bowser, with Uka Uka stating Gigadark Bowser is actually being successful, something the villains never could do. After Gigadark Bowser is defeated, Uka Uka throws a temper tantrum at being defeated. During the second arc of Season 21, Uka Uka holds a meeting, where he chews out the villains for their constant failures, stating that Yami Bakura, Ganondorf, and Patient Zero are more successful than them. Uka Uka then listens to Ripto's suggestion of recruiting more villains to help them. Uka Uka later goes into the past with Yami Bakura for "the ultimate Shadow Game". In Season 22, Uka Uka has Ganondorf, Yami Zelda, and Yami Kirby enter the tournament while Yami Bakura recuperates. During the course of Season 22, Uka Uka is forced to work with the heroes when the villains are betrayed by Wiseman. Later, Uka Uka is left behind after Samus absorbs Yami Bakura's corpse, therefore losing his control over the villains, and unintentionally reveals Master Hand and Crazy Hand's true colors. Uka Uka later manages to get back in Samus' good graces, and begins to lighten up due to the villains' success. Later, Uka Uka watches in horror as both the Time Eater is destroyed and Samus is killed by Gohan. Uka Uka ultimately has a nervous breakdown and is locked up at the asylum in Smash City. When Wiseman launches his escape plan, the depressed Uka Uka is left behind. Uka Uka is later nearly left behind during the second breakout, until he finds the Millennium Ring and hears the voices of The Offspring of Zorc, which pleases Uka Uka who then breaks out himself. Uka Uka then confronts Thanos and Nebula after The Dark Surfer leaves, and takes Nebula with him. In Season 23, Uka Uka tries to defeat Mechtavius Destroyer, but the evil mask is shattered by the psychopath. Uka Uka's death is confirmed due to his absence during the Fight to the Finish 2 Arc, which features every major character in the series. However, Uka Uka is revived and integrated into Mechtavius Destroyer. In Season 30, Uka Uka plays a more supportive role, as he helps Silver realize that Giovanni truly does care for him. In Season 32, Uka Uka is betrayed by the League of Villains and is used as a power source by Dr. Eggman for his latest weapon.
- Uka Uka uses his original appearance in Super Smash Bros. Crossover, as that is the form he is most recognized in.
- Uka Uka is one of the few characters that are more sadistic than Yami Bakura because while Yami Bakura wants to use the heroes in his plans, Uka Uka wants them destroyed outright.
- Uka Uka is one of the most insane characters in the series, as he didn't care about what Gigadark Bowser would do to the universe, as long as he caused destruction. However, in Season 30, Uka Uka is against Mechtavius Destroyer due to the threat he poses, since he would leave nothing for Uka Uka to destroy.