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Pokemon X and Y Pokedex: Mega Mewtwo Y
Mega Mewtwo YMega Mewtwo Y was the first Mega Pokemon unveiled. It gains the Insomnia ability when it Mega Evolves, which prevents it from falling asleep. It's exclusive to Pokemon Y and evolves with Mewtwonite Y.

Vitals
Type:Psychic
Height:4' 11"
Weight:72.8 lbs