Birdo was the heroine in the game: Wario's Woods, a puzzle game released for the NES. The woodland monsters were attacking the Mushroom Kingdom, and Birdo, along with Wanda and Toad, went up against Wario.
Although Birdo is not playable, she aids Toad by giving bombs to Wanda, who then passes them to Toad. If the player took too long to complete a level, Wario would grab Birdo. She will also shout instructions and encouragement to Toad from the corner. The instruction manual for this game calls Birdo Catherine, which is the character's original Japanese name.