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".