At the title screen, press up, L, B, and A at the same time to access a password screen. Enter any of the codes listed below. When you're finished, press B button many times to exit the password screen.
Unlock Climbing Race 5 in Jungle Jam: 55860327
Unlock Obstacle Race 4 in Jungle Jam: 35805225
Unlock Attack Battle 3 in Jungle Jam: 65942922