Parodius: Power-up ship:
Pause game play, then press Up(2), Down(2), Left, Right, Left, Right, B, A.

Parodius: Music test:
Press Up(2), Down(2), Left, Right, Left, Right, B, A at loading screen

Parodius: Bonus level:
Locate the gap at the bottom of the screen on level 3 soon after entering the cave. Enter it to advance to a secret bonus level.

Track And Field: Bonus effects:

Hammer toss
Throw the hammer at maximum power at 80 degrees to hit a UFO.

Triple jump
Land just short of the pit and a frog will appear on the screen.

Archery
Hit the ground between the 40 and 50 yard marks in the 70 yard shot to see a groundhog.