Level select:

Hold [Ctrl] + [Option] + [Command] when selecting the number of
players. A level select window will appear to allow any level from 1
to 20 to be selected.

Cheat mode:

Enter one of the following codes to activate the corresponding cheat
function.

Effect Code

Use one life from other player to
resurrect self 1ammybrother
Etra TNT box 1ambubbus
Etra lives 1amcheater
Kill everything on screen 1ampesticide
??? 1amfrostydog