Level Skip:
Level 2-C76564J
Level 3-L88R8TC
Level 4-Y539WZG
Level 5-NTTJ9KY 

Original Batman Suit:

Pause the game then hold the L button while pushing C-Left, Down, Up, C-Right.

The screen will shake if down correct.

Flight Mode:

Pause the game and press Up, Down, Left, Left.

Thanks to Revolution reader Cornbread!