Various Codes
While playing the game, pause and enter the code:

Code - Result:

L R Left Left Up Up - Disable Time
Right Right Right Left Left Left R L - Kingsize Pickups
L L R R Down Down - Skip Stage

Stage passwords:
Stage 1 - Wakko, Wakko, Wakko, Wakko, Wakko
Stage 2 - Dot, Yakko, Brain, Wakko, Pinky
Stage 3 - Yakko, Dot, Wakko, Wakko, Brain
Stage 4 - Pinky, Yakko, Yakko, Dot, Brain
Stage 5 - Pinky, Pinky, Yakko, Wakko, Wakko
Stage 6 - Brain, Dot, Brain, Pinky, Yakko
Stage 7 - Brain, Pinky, Wakko, Pinky, Brain
Stage 8 - Brain Pinky, Pinky, Wakko, Wakko
Stage 9 - Dot, Dot, Yakko, Pinky, Wakko
Stage 10 - Brain, Dot, Brain, Yakko, Wakko
Stage 11 - Akko, Yakko, Pinky, Dot, Dot
Stage 12 - Pinky, Pinky, Brain, Dot, Wakko
Stage 13 - Yakko, Wakko, Pinky, Wakko, Brain
Stage 14 - Pinky, Wakko, Brain, Wakko, Yakko
Stage 15 - Dot, Pinky, Wakko, Wakko, Yakko