Just to tickle your fancy with some examples: Sonic 2 was going to have a level called Hidden Palace Zone, Super forms were never meant to be used in the first games, Sonic 3D was made after a game called Sonic Xtreme was canned, and Sonic Jam's Sonic World was a prototype engine of Sonic Adventure 1.

Hey segaloco don't advertise that website you mentioned. It's in the rules can't advertise in posts lol. If you want to advertise you may place a link on your sig.

Okay okay, its just kinda hard to reference prototypes (my main expertise) without referencing Retro in any way. I guess I can still share my knowledge.

I see. Hmm, alright you may mention them as long as theres no links involved lol ok?

Speaking of prototypes, has anyone played some of the more obscure ones (like Sonic's Edusoft for Master System or the S3K (when it was still just Sonic 3) combined beta)? I've played a few myself.