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[[File:Jessie Mimikyu Disguise.png|thumb|left|200px|Disguise activated]]
Mimikyu first appeared in [[SM003]]. When the [[Team Rocket trio]] was walking through a forest on [[Melemele Island]], it jumped out of some bushes, scaring them. They initially believed it was a Pikachu. But when the head of its costume fell askew, they were scared yet again, initially thinking the Pikachu's neck was broken. [[Meowth (Team Rocket)|Meowth]] ascertained that it was not really a Pikachu, but quickly determined that it was creepy, refusing to translate its clicking-type speech. Even [[Jessie's Wobbuffet|Wobbuffet]] was acutely frightened by Mimikyu. Thinking it was a little cute, [[Jessie]] decided to catch Mimikyu anyway. Having no Pokémon yet, since she left [[Jessie's Gourgeist|Gourgeist]] in [[Kanto]], she threw Meowth at Mimikyu, commanding him to do [[Fury Swipes]]. He connected, but it did no damage due to Mimikyu being a Ghost-type. Meowth continued to be scared of what Mimikyu was saying and demanded it take off its costume to fight him "fair and square" When he tried to unmask Mimikyu, it badly hexed Meowth,
suffering a near-death experience. Jessie and [[James]] were able to wake Meowth up by dumping buckets of water on him. After relating his near-death experience, Meowth blamed Mimikyu for the hex.
Before they could do anything about it, Team Rocket hid after hearing something approach. It was [[Ash Ketchum|Ash]] and his classmates. Upon seeing Mimikyu, the [[Rotom Pokédex]] related a story of a researcher having died from shock after trying to peek under a Mimikyu's costume. Having noticed [[Ash's Pikachu]], Mimikyu became enraged. Ash attempted to catch Mimikyu, but Pikachu's [[Iron Tail]] had no effect due to its Disguise ability. Mimikyu then beat up Pikachu using [[Play Rough]]. Before the battle between Pikachu and Mimikyu went too far, Team Rocket stepped in, determined to catch a Pokémon who was effective against Pikachu. Meowth jumped at Pikachu with Fury Swipes. But when Pikachu tried to counter with [[Electro Ball]] on his enemy, Mimikyu intervened and deflected it with [[Shadow Ball]]. Speaking through Meowth, Mimikyu told Team Rocket that it would help them against Pikachu, expressing a deep-seated hatred for it. Before it could resume fighting Pikachu, however, a [[Bewear]] kidnapped Jessie and James. Meowth was able to get Mimikyu to disengage, and they chased Bewear.