You can skip to Buttville by pausing the game and pressing l,a,up,r,a,r,a,select. You can skip to Down the Tubes by pausing the game and pressingup,l,down,a,r,a.
You can skip to For Pete's Sake by pausing the game and pressing r,l,r,l,a,r. You can skip to level five by pausing the game and pressing r,l,a,b,b,a,l,r. You can skip to Snot a Problem by pausing the game and pressing r,up,select,l,r,left.
You can skip to What the Heck by pausing the game and press select,r,b,down,l.
PS: I forgot what the name of level five is.
This has been another great cheat by supersaiyanraditz! Hoorayyyyy!