At Title screen, press Up, Down, Left, Left, Circle, Square, Triangle, X, X, X, Left, Up.
At Title screen, highlight the "Bonus Mode" option. Hold L1 + R1 and press Start. Now an "Animation Test" option will appear under "Voice Test" at the "Bonus Mode" menu.
Get the exit and go to Clownman's level. Kick the megaball into the clownface on the arch at the beginning and a extra life will come out. Exit and do again and again.
Thanks to Revolution readers Jason Artibee, Ian MacFarlane and neon!