Not sure if it's known or not, but hey it's worth a shot. One day I was bored and entered Sonic 3's competition stages while in debug mode, and while cycling through objects, I found spikes. I don't recall seeing any of these anywhere in these stages so this seemed pretty odd to me. Here's a pic Again not sure if it's known but I don't recall ever reading about it anywhere. Edit: Just noticed the screwed up HUD from the 1 player zones too, crazy.