This a video featuring the developer behind the game Sonic 3D Blast. I had never heard of this "secret", but about 25 seconds into the video, I knew exactly what was going on, and it is brilliant. I suspect other developers will have the same "aha moment" when he starts describing what's going on. And if you are newer to software development, this is a classic example of what it takes to ship software sometimes.
I'm not a game developer, but I can already think of ways I could implement this type of hack in my own code. Hopefully I won't have to though.