Play as Eggman in Sonic 1. Impressive technical feat considering the year it was released, it required reworking the mappings and collision engine from scratch in order to fit Eggman's sprites in. Very buggy.
By using SonED, LOst Library and Hivebrain's disassembly, LOst successfully restored the planets in Marble Zone as they were during the game's development.
Hack that adds a number of extra features like spindash, specific shields, a continue feature and more. Also includes a new level, Jungle Zone, which is a remake of the original 8-bit version of Sonic 1.
After the much-anticipated release of SonED2, Stealth shocks the community once again with this gem of a hack - Knuckles in Sonic 1. The name says it all and even more: this includes gliding, climbing and spindashing!
A few days after the release of this hack, Stealth released another version - dubbed "revision 01" - that fixes a couple of bugs and sports a completely new feature (only accessible by a code); Read the end of the readme for further information, as it is worth a try.
Tails in Sonic 1. It says everything. It flies, it spindashes, there's no sign of Sonic in the game. This is an update by Puto, which fixes alot of bugs.
Uploaded upon request, this hack was made during drx's disassembling of the Sonic 1 ROM. There is no title screen, has purple flowers in Green Hill Zone, among other things that make the hack seem like an early prototype.
Play with Sonic, Shadow, Mighty, Tails, and Knuckles in this high speed hack of Sonic 1. All the music has been changed, as well as the palettes. There is a new layout, and a bunch of ASM changes. Version 4.0b shows the game ported to the Sega CD, and introduces several new features. The ISO linked here is for US Sega CDs.
A proof-of-concept showing Green Hill Zone and Emerald Hill Zone running on the Sega CD, where you can play as Sonic, Tails, or Knuckles. The ISO linked here is for US Sega CDs.
Grab that Sega Mouse or Sega Mega Mouse you got with Art Alive or Wacky Worlds, respectively, and get ready to play as Sonic in this control system mod. Hint: Kega Fusion also has mouse support.