In Episode 17 of Season 3, (the one where the drug addict comes back, and where the janitor pretends he has a twin brother), the scene where the janitor puts the tape into the TV to show J.D. and Turk his birthday with his "twin brother", look closely when he puts the tape into the TV. It clearly doesn't go in at all, showing the TV isn't even on. You can still see the tape hanging out of the slot after the tape is "played".