Bonus level
Enter BL26 as a password
Level skip
Enter 99BB as a password, and ignore the error message. Press Start + Select to advance to the next level. Press Start + A to advance to the checkpoint within that stage.
Password - Level
9LKK - 1
BL26 - 2
5P9K - 3
6652 - 4
BKK2 - 5
2PLB - 6
6562 - 7
L59B - 8