Find and read the "Day of the Kungfu Zombies" books in various levels. When you look at this book, it will not highlight an action response. You must search for the book, then press Action to read it. Your character will say "I know Kung Fu?", then a tattoo will appear on your hands. Your hands will now be stronger, and can kill zombies.

Alternately, quickly press Right, Down, Left, A during game play.