Stand directly under the trees and kick the ball straight up the tree trunk on various levels in the game (the original author was not too sure which they might be however). You'll notice it flash slightly if there's a special icon to be found in that tree. You must first kick the ball up into the tree and hit the hidden icon four times. Do so and you'll receive an extra 4,000 points. If you can now repeat this process and hit the icon another four times, you'll uncover the special icon's identity. The icon types vary from invincibility to speed boots. Just collect them and away you go.