You can get Joe to whistle parts of the Super Mario Bros. main theme if you have a Shocking Pink item (the pink bombs). To use them, hold down the kick button—Joe will kick out one and bounce it on his foot until you release the button, which makes him kick it away. If you don't release the button, he'll keep juggling the bomb with his foot, then start whistling the six-note intro to the SMB theme. If you jump in the air and do it, he'll start to whistle the "chorus" of the theme.