To do this, you need 2 players and the bucket that is in the castle. You need to have both players grab the bucket, then go into the hole where you get up (legitimately) while holding the bucket, and the game glitches out! Your arms go crazy, and the screen turns white.
If you pause and try to load the checkpoint, the screen turns black. Same if you try to reset the level.
If you quit to the menu, the screen will still be black, with the menu text around it. (THIS BREAKS THE GAME! TRY AT YOUR OWN RISK! YOU WILL NEED TO RESTART MANUALLY!)