I'm kinda hoping I got this one right so I can pat myself on the back for catching an obscure reference.
King's Quest 7: When you end a conversation with Auntie Biotic, she warns you not to mail any wooden nickels. In KQ7, there was a seriously bugged wooden nickel that would make the game lock-up when you obtained it, and even after that, it was still screwed up so you couldn't give it to the person you were supposed to give it to.