The recent Sonic 2 GG autodemo made me think of this old prototype of Sonic 1, released IIRC by 2004: http://info.sonicretro.org/Sonic_the_Hedgehog_%28Game_Gear_prototype%29 Since it is commented the Game Gear port of Sonic 1 is based off the SMS version, my curiosity took me to use the SMS PAR Codes in this early GG Proto. The result is that I can access some deleted / garbled data, which will sometimes reset the game, or display black / blue screens, or in the best case take you inside the level. Some places are pretty recognizable, even with the garbled tiles and objects. Some are not recognizable and may produce some strange effects as causing Sonic to be unable to jump or to be stuck in his rolling pose, life monitors being carried away, strange platform structures, and a completely f***** up try to the ending sequence. As I don't have much time to describe better all the sequences of this video, it is being provided as is. Well, it is pretty easy to try it on any emulator using the PAR codes listed here: http://info.sonicretro.org/Cheat_Codes:Sonic_the_Hedgehog_%288-bit%29 EDIT: Trying to embed YT video. There's also a brief description at the video page.
I remember accessing Jungle and a few other levels back when the prototype was released and assuming that the garbled stuff was just due to the graphics not yet being adapted to the Game Gear's color depth... but I haven't seen a monitor being carried away since Sonic CD. Would it be possible to just copy-paste the level data from that ROM to the SMS game, to check if things show up correctly? Perhaps that monitor-carrying thing will turn into something recognizeable.
There probably isn't a monitor-carrying thing - it's the same monitor that appears on a conveyor belt in the final game.
I'll let this to the ubber hackers in house, if there be interest, as I have very basic hacking skills. It would be very interesting a few more information about this prototype. A conveyor belt would move both monitor and Sonic, but Sonic is not being carried away. Anyway, I can't jump or roll in this long platform (when he does not already fall rolling, in this case I can't stand up).
The conveyor belt doesn't move the monitor at all; the monitor is coded separately to move until it runs out of ground and then fall.
Nice observation about the moving monitors. One of these appears sometimes at the last boss screen (Sky Base 3), but this time you can get it.
