If you get Game Over, you can still continue on the level you were last on. At the title screen, press B, 7 times, A, 7 times, Up, 6 times, then Start. Alternatively, instead of pressing Up, 6 times as part of the sequence, press Up, 7 times and you will get a sound confirmation and the same effect.
At the title screen, hold B on Control Pad 2 and press Start on Control Pad 1. The D-Pad controls will now be reversed.
At the title screen, press A + Start.
To view the credits, you first have to sit through all 6 demo sequences, whick takes over five minutes. Then at the title screen, press A, A, A, A, B, Up, Up, Down, Down, Down, Down, Down, Down, Start.