Birdo

Birdo is a strange creature that first appeared in Doki Doki Panic (aka. Super Mario Bros. 2). According to the instruction manual, he is a boy that likes to be called Birdetta. However, in the credits, Birdo is shown as Ostro, which is another type of enemy which is nothing to do with Birdo.

In later games, Birdo has been female (rather than a male who wishes to be female), and also seems to have become Yoshi's girlfriend in some games, proving that Birdo is definitely female.

In Mario and Luigi: Superstar Saga, Birdo replaced Bowser as Popple's assistant. She seems to have fallen in love with Popple.