At the "press start button"/title screen, press L, U, R, D, D, R, R, U, and RT. Use U or D to select your starting room.
999 Lives: [submitted by Jon Garin]
At the "press start button"/title screen, press U, Rx9, Dx6, Lx7, Z, X, Y, Y, Y, and Z which will make the music reset and begin from the beginning. You can then either start a normal game, or execute the Room Select code to start at a different level.
Attic Short Cut 1:
In the "Attic", Stage 1, first off, grab the spring and drop it to the right of the first short platform. Jump off of this, up and to the right and walk across to grab a 1-Up. Then jump back down and grab the spring again. Holding the spring in front of you, go to the right and bump all of the enemies (without letting go of the spring). This will kill all of them without you getting any damage. When you get to the first lock-box, jump over and drop the spring against the wall. Jump off of the spring and push to the right. Walk above the screen and you will drop in front of a second box. Enter this box for dozens of clock-ups, a 1-Up, and a boost up to 4 cogs. Go out the second box and you will find that you have skipped a small part of the stage.
Attic Short Cut 2:
In the "Attic", Stage 2, first off, go to the last box at the end-right and enter. This will take you to a room full of clock-ups for you to grab. Then exit this and you will find yourself back at the beginning of the stage. Now, go to the next to last box at the end-right and enter. In this new area, first, go to the left and grab the key and open the door. Then go back to your right and you will need to stand on the first pile of boxes while holding one of the dynamite sticks. Throw the dynamite up and when it explodes, a second key will fall down. Grab this key and go back to the left and open the second locked door. Enter the cage and you will be warped directly to the Attic's boss.