Enter the following at the password screen:
MYSTIC - Dogsville
LEDZEP - Loony Moon
WOOPIE - Planet K-9
REEVES - Planet Wierd
PIXIES - Plant Foggia
ANKLES - Scrapyard
Amiga:
Endless level:
Enter a hidden bonus room, then use the cursor keys to move around. Note: The up and down directions will be reversed. Scroll the screen to the far right and allow Wonderdog disappear off of that side. Your character will appear back in the main game, however he will walk to the right in an endless level.