Birdo

Birdo, known in Japan as Catherine (キャサリン, Kyasarin, [kja.sa.ɽĩ.ɴ]), is a fictional character in the Mario franchise. Her first appearance was as an enemy in Yume Kōjō: Doki Doki Panic, which was localized for English audiences as Super Mario Bros. 2. Since then, Birdo has been a recurring character in various franchise spin-offs. Initially, she was depicted as an antagonist, but has since been depicted as an ally. Birdo has also made several cameos, particularly in the Mario Kart series and the Japan-only Wii video game Captain Rainbow.

The original manual for Super Mario Bros. 2 asserts that Birdo is a boy, who "thinks he is a girl", and would rather be referred to as "Birdetta". Later releases of Super Mario Bros. 2 lack mention of her gender in either the game or the manual. Nintendo eventually retconned Birdo as female, first in Mario Tennis which depicted Birdo and Yoshi as girlfriend and boyfriend. However, several games portray her as male, such as Captain Rainbow, or refer to the gender confusion without assigning one, such as in Super Smash Bros. Brawl.