From Sonic Retro
Unused Characters
Using a hacking tool called WiiRD revealed several unused playable characters in the Wii version of Mario & Sonic at the Olympic Games: Birdo, DK, Silver, and Jet[1]. The Birdo model doesn't seem to be finished because the mouth seems off. Also, several other characters that were used as background characters can be made playable also. These characters are: Shy Guy, Toad, Cloudy, Charmy, Espio, Cream, Boo, Bullet Bill, Goomba, Heroes Enemy 1, Heroes Enemy 2, SA1 Monkey, and Big. These characters can only be used in certain places such as the trampoline event.