Bonus characters:
Win all the races under the easy difficulty setting to unlock Mystery Rider.
Successfully complete the game three times to unlock Phil and Lil from "Rugrats", Sid from "Hey Arnold!", Doug from "Doug", and Otto from "Rocket Power".
Plankton and bonus track:
Successfully complete the game once to unlock Plankton and a bonus track.
Quick start:
Hold [Up] when the pre-race timer reaches "3".