The Sonic 3C 0408 prototype appears to have data from older S3C builds leftover in the padding area. I haven't searched through this very well as there is quite a bit of data here and my methods are lacking, but I was able to stumble across a couple interesting finds. It's surprising that no one has really seemed to go through any of this as this prototype has been available since 2008. A particular reason for interest here is the nearly 5 month development gap between retail Sonic 3 and 0408 that we know very little about. On the left is an earlier version of the Death Egg sprite seen at the end of LRZ2. It's using the colors of the enemy palette line ($01) and the shading differs in areas. The final sprite is on the right for comparison and is rendered on the same palette line as the rest of the level graphics. It is also shaded a little differently. I did my best to reconstruct the early sprite as well as possible. Next, we have an earlier design for the Eggrobo badnik, which I thought was exclusive to an older build, but is actually used regularly in S3C 0408. I've never seen this documented anywhere. Notable differences here compared to the final include the eye, and the position/length of the arm. I wouldn't be surprised if there is more to look through. Other things I found odd were a version of the Red Eye miniboss graphics that seem to be grouped with the DEZ Act 2 boss, along with smaller art set for Mecha Sonic. The leftover data in the ROM appears to start at 0x80000 and user Jorge Nuno listed some rough offsets on the HP discord server: Keep in mind there is more than what is listed here. I apologize if this topic belongs somewhere else.