Mirage Mew is an artificial psychic-type Pokémon created by Dr. Yung using the Mirage System, holographic technology designed to generate Pokémon from data. Unlike other Mirage Pokémon, it possesses self-awareness and emotional capacity, traits its creator dismisses as flaws. Dr. Yung disowns it for disobedience, labeling it a "flawed specimen."

Initially observed watching battles from afar, it exhibits curiosity and reluctance for direct engagement. Following Dr. Yung's kidnapping by the Mirage Master (later revealed as Yung himself), it interacts with protagonists Ash Ketchum and Professor Oak. It shows self-preservation instincts when attacked by Mirage Magnemite but displays no aggression toward humans or Pokémon.

Its development centers on forming bonds with the heroes. After Ash saves it from a damaged generator, it guides him through the Mirage Mansion, revealing its artificial nature yet distinct sentience. It demonstrates concern for others, alerting Ash to Misty's peril and later intervening to protect Pikachu and Professor Oak's Dragonite from Mirage Mewtwo's attacks.

During the climax, it blocks a lethal Hyper Beam aimed at Pikachu, an act of selflessness that enrages Dr. Yung. Mirage Mewtwo overwhelms it with physical strikes and a dual Solar Beam, dissolving it back into data. It later reemerges embedded within Mirage Mewtwo's code, restraining the entity to enable Pikachu's decisive Volt Tackle. This action destroys the Mirage System and consumes Mirage Mew permanently.

Professor Oak concludes its sentience and soul—qualities incompatible with pure data—caused the system's destruction. Its sacrifice and defiance of programming to protect others starkly contrast Dr. Yung's view of it as defective.