Get 50 Rings in all 6 Zones in either Act 1 or Act 2 and a Special Stage will appear. To get the Emerald in Game Land, you must win the race against the CPU with 50 rings.
Infinite Boost
Get all of the red rings in every level and mission to unlock an infinite boost option in the game. Note: Cheat not available in Versus or Time trials.
Nega-Mother Wisp
Complete Terminal Velocity with all emeralds. After the credits are over, return to the game. After a quick cinematic, and the final stage with Nega-Mother Wisp will be available at the very top of the world map.