Level select
Hold [Option] and select the one or two player selection at the title screen. Note: High scores will be disabled.
Christmas music
Set the Macintosh system date to December 25 and begin game play.
Birthday greeting
Set the Macintosh system date to January 20 and begin game play. The game will wish Dave Wareing a happy birthday. Look in the box that flashes the "Please Register" reminder. It will eventually say "Happy Birthday David".