Croc

Level select:
Enter PQHPBFDHJB as a password.

Super password:
Enter CPNGTQRNFL as a password to unlock all levels (including the jigsaw level), secret doors on each world, and 4 Gobbos collected from each world.
The secret doors give you access to the mini-games from each level, but a Gobbo obtained here will not be recognized in the main games.
However, the Boss levels have not been completed.

Hint: Mystery head:
On level three, there is a part where there are platforms to climb up a hill.
On the bottom platform is a dip, or, a pit.
In the pit, you can see a rock with a face.
It appears to be a crocodile face, but others say that it looks to be a face with a hat on or even a mushroom.