Unlock super characters:
     Finish  World  1  -  9  with only one particular monkey
(either  Baby,  AiAi,  GonGon,  Doctor,  MiMi, or YanYan) to
access to the "Super" version of that character.

Unlock Staff Credits mini-game option:
     Finish  1st World then go to the Options menu to access
to the Staff Credits mini-game option.

Unlock World 9 (Sinking Swamp):
     Finish Worlds 1 through 8 without using a single continues.

Unlock World 10:
     Finish World 9 without continuing.