Android 18 is an android created by Dr. Gero, a former fighter at the Glitz Pit, and a neutral character in Super Smash Bros. Crossover since, despite helping the heroes on occasion, she does not actively fight for either side, much like her brother, Android 17, though Android 18 and Android 17 become protagonists by the Time Eater Arc. In Season 23, however, Android 18 is bitten by Sakura Haruno while she is infected by the creepypastas. As a result, Android 18 is turned into a vampire, and since Sakura was infected by the creepypastas, Android 18 goes beserk at the scent of blood due to split personality. This event, along with Shadow the Hedgehog's death, causes the heroes to reject the Dark Heroes of Legend. Android 18 is later used by BEN to complete his metamorphisis and release the creepypastas from their prison. Afterwards, BEN decides to transform Android 18 into a new form, with the evil on the outside instead of the inside, turning her into Super Android 18. Super Android 18 later joins forces with Tikal and Chaos during the Fight to the Finish 2 Arc. Later, Super Android 18 is the only villain who isn't absorbed by Mechtavius Destroyer after he blasts the heroes out of the Hyperbolic Time Chamber. At this point, Android 18 appears to be showing remorse for her actions. This is somewhat proven when Super Android 18, despite her transformation, sacrifices herself to save her former friends, though it has yet to been seen if this remorse was genuine. As a result, Mechtavius Destroyer absorbs Super Android 18. Later, Super Android 18 is seen with the villains, meaning her good heart was free for a moment before being overwhelmed by evil again. Eventually, it is revealed that Android 18 has become corrupted by the creepypasta essence that infected her, and she subsequently kills Android 17 to gain his power. In Season 24, Android 18 undergoes a metamorphisis to completely adapt to her new power. After the metamorphisis is complete, Android 18 heads to Smash City to destroy Naruto Uzumaki, Goku, Sonic the Hedgehog, Vegeta, Dan Kuso, and Drago for their part in the destruction of Mechtavius Destroyer. However, it is revealed that the corrupted Android 18 is actually Tikal in disguise, with the real Android 18 having been restrained by tree roots. Android 18 wakes up shortly after Fleetway Super Sonic finds her, but with no memory of what happened prior to her transformation. Since Drago altered the past, Android 18 was never transformed, since BEN no longer exists. However, it is revealed in Season 30 that Android 18 still has the capability to transform into her Super form.
Android 18 is depicted in her third outfit during the Android/Imperfect Cell Saga. When Android 18 goes beserk due to her vampiric instinct, her hair becomes messier and her eyes become the same color as Gigadark Bowser.
After becoming Super Android 18, Android 18's appearance changes radically, with longer hair and a completely different outfit. When Android 18 reveals the truth behind Amy's defection, her outfit changes into an outfit similar to that of Zombie Zelda, and her eyes become the same color as Gigadark Bowser's once again.
After her metamorphisis, Android 18 wears an outfit similar to the one Alice Gehabich wears exclusively in Super Smash Bros. Crossover when she isn't Masquerade. In addition, Android 18 becomes buffer as a result of the metamorphisis.
Android 18 is witty and sarcastic. Android 18 is also greedy, since she forced Android 17 to resign from the Glitz Pit due to the low prize money. However, Android 18 knows what's right, as she saved Itachi Uchiha and Sasuke Uchiha from drowning, though she was unaware Sasuke became a criminal again. After being turned into a vampire by Sakura, Android 18's personality is the same unless she smells blood, as this causes Android 18 to go beserk as she is overwhelmed by vampire instinct, but she retains her wittiness. However, prolonged exposure to the creepypasta essence has corrupted Android 18 completely, turning her into a crueler person and somewhat of a successor to the Pecking Order. Android 18 also has no more sympathy whatsoever, as she absorbed Android 17 to gain his power for herself.
- In Super Smash Bros. Crossover, Android 18 is a kleptomaniac, as she stole Chazz Princeton's wallet when he wasn't looking.
- Android 18's temper is exaggerated in Super Smash Bros. Crossover, as she tore Jolene's office apart out of fustration of the low prize money.