The Giant Mouser at the end of level 4 can be beaten even more easily than normal with this trick. Just stand under him and wait for his mouth to open. When his mouth opens to reveal the "weak spot", pause the game. Unpause the game, and the Mouser's mouth will be closed again, but his weak spot will be slightly visible from behind his mouth. You can now hit it to cause damage while his mouth is closed! Repeat this every time he opens his mouth for an easy victory.