Whenever you finish off a level and the name of the next level is on the screen, hit 1 and 2 alternately about 25-30 times total. If you are fast and don't double hit one of the buttons, you'll get ...

Hitting small animals produces coins. Keep hitting an animal for more coins! You can get 7 coins from an animal. To unlock this final challenge, beat all 4 main worlds (GPU Jungle, SSD Speedway, ...

my friend stole this out of the walmart discount bin and gave it to me as a joke. little did i know it was actually a really good game.