Unlock the Secret Characters
There are 4 hidden characters that can be unlocked:
Drumstick - Fling a frog up to the green sillouette shaped frog picture in the world map (left of Wizpigs face). Stomp on the frog that comes out.
T.T - Beat all of his ghosts in Single Player Race. It doesn't include the new unlockable stages.
Taj - Complete Adventure 1.
Wizpig - Complete Adventure 2.
Unlock Adventure 2
Complete everything in Adventure 1. After the second Wizpig race in space and the credits, you'll unlock Adventure 2.
Super Boost
Before landing on a zipper or using a blue balloon, let go of the acceleration button to get a much stronger longer lasting boost then normal.