The first appearance of Birdo was in Super Mario Bros. 2, where Birdo would appear as a mini-boss character of various levels, serving the evil Wart, as he enslaved all of the creatures of Subcon.
She, depending on the form, spat eggs, fireballs, or a combination of both at the player. Birdo's standard pink form fired eggs, a red color swap shot both eggs and fireballs, and a green Birdo sent only fire after the characters. In the event of a green Birdo, the player had to find a Mushroom Block to toss at Birdo. Rarely, a Birdo would appear as a common enemy, instead of a boss. These Birdos are, in a way, invincible, as after the player defeats one of these Birdos, they come right back. The credits of Super Mario Bros. 2 label Birdo as Ostro, and vice versa, a different enemy that has nothing to do with her. To defeat Birdo in Super Mario Bros. 2, one has to jump on Birdo's eggs and throw them at back at her.