Select "Credits" from the "Help & Options" menu and watch the whole thing.
Complete a level without killing any Scientists.
Splode 300 times in a single level.
Complete the Single Player game in Hardcore mode.
Release The Maw from his cage and send him into space.
Eliminate 10 Scientists and stop them from spreading their filthy lies.
Change the controls around in the "Controls" menu.
Complete the Single Player game.
Complete the Multiplayer game.
Create 5,000 filets.
Collect all 47 cakes in Single Player mode.
Collect all 47 cakes in Multiplayer mode.