I remember a couple years ago I put Sonic 3D in my Genesis, turned it on, and either before or after the "SEGA!" logo this screen flashed and said something like "You have accessed the secret (either level select or stage)!" and proceeded to freeze.
I was about 10 years old when this happened, and it never happened again. I'm not sure if it's real or not, but I definitely remember something like that happening.