Simplify the following text for a Grade 6 native English-speaking person.
Original: Birdo , known in Japan as Catherine , is a fictional character in the Mario series of video games , who first appeared in Yume KÅ jÅ : Doki Doki Panic , which was localized for English audiences as Super Mario Bros. 2 and is an enemy to Mario .
Simplified: Birdo is a character in the Mario series . Birdo first appeared in Super Mario Bros. 2 .