Unlock Level Skip:
Enter Taz, Elmer, Daffy at the password screen and to during gameplay press Start then Select to skip levels.

Level Passwords
Select Options at the Title screen and then go to the Passwords menu and enter the following codes to unlock the corresponding level.

Start from Level 2 - Easy:
Daffy, Elmer, Taz

Start from Level 4 - Easy:
Sam, Elmer, Daffy

Start from Level 2 - Hard:
Taz, Sam, Marvin

Start from Level 4 - Hard:
Marvin, Sam, Taz