Mario & Sonic at the Olympic Games is a sports game that places Mario, Sonic, and their various allies against each other in Olympic events. The game has the official Beijing 2008 Olympics license, and features environments based on actual Olympic venues.
Birdo, along with Donkey Kong and many others, were originally going to appear as playable characters in this Olympic Game, but were scrapped from the final product for unknown reasons. Additionally, she is the only scrapped character with an incomplete model. The Birdo model doesn't seem to be finished because her mouth seems off. Also, using a hacking tool on the game, revealed several characters including Birdo and Donkey Kong that can be playable too.