I know about a special glitch in Super Mario Bros. 2 (the NES version). Here's how it works:
Toss a Red Potion to open the door to Sub-Space as usual... Then, while you're in Sub-Space, collect some Cherries in order to get a Star. Get the Star while you're still in Sub-Space, and if you still have the Star power when the Sub-Space world disappears, the Sub-Space (Super Mario Bros.) music will start playing on the normal game screen!
I think that's how it worked...
------------------------------
"Bwa ha ha! Guess who it is, loyal Mario fans...
It is I, King Bowser... ruler of all Koopas, big and small. I have come to take over the Mushroom Kingdom (no, not the place...I mean the WEB SITE!)! Deezer, you will surrender your troops to me, or else you will never see your precious Mario again! Bwa ha ha ha ha ha ha ha ha ha!"