Here is a list of easter eggs in the game. (They all work for both cd and nocd versions)
Level 0 : Jump past the spikes. Walk off the screen. There will be a pit full of jumping people. Don't jump in, or you will be stuck.
Level 1 : Move the crate to the right edge of its platform, but not off. Jump on it and jump as far right as you can. you will jump over the wall! Jump into the edge of the screen. There will be a secret room!
Level 2 : If you look very closely, at the start, there is a greyscale head flying across the screen!
Level 5 : The title of this level will be whatever text is copied to the clipboard (select text and press CTRL+C or COMMAND+C).
Level 7 : If you look very closely, you will see a crate under the level to the right.
Level 8 : You can collect as many coins as you want, although you only need 10. (20)
Level 14 : This is probably the most popular easter egg. Hold 'R' until the level number changes to "XX". You are now in the secret cactus level. It is impossible to beat, so just press 'ESCAPE' to exit.
Level 25 : Not much, but you can jump from the highest wall of the 3rd corner to the 4th corner without the button and vice versa.
Level 30 : SPOILER ALERT! Select to read --> Instead of having to move the mouse at 50 miles per hour, you just need to spawn your character UNDER the stage.
Level 55 (I Bet this is not the Final Boss) : SPOILER ALERT! Select to read (next line).If you spawn a boss inside the wall, the ceiling, or the ground, it won't hop.
Please tell me if I missed anything.
Edited by MarioLuigi2010, 13 December 2010 - 11:00 PM.