Easy coins - When you go to the beach, there should be a series of dots in the sand. Join them up into a circle. A number of coins will fall. Collect them all. Keep repeating this until it no longer accepts the dots joined up.
Hidden characters that can be unlocked
T.T Complete all of his ghosts in Single Player Race. It DOESNT 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
Opening the Cracked Wall - When you start, follow the track round until you go in a tunnel. In here, there is a cracked wall with a picture of Wizpig. Draw round Wizpig's head (ears included) and the wall should smash open. You must be quite accurate and it may take a few attempts.
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.