Kirby in Sonic the Hedgehog 2 is a hack of Sonic the Hedgehog 2 by Lone Devil (Also known as Darkon360) for the Sega Genesis/Megadrive. It features Kirby and Waddle Dee whom replaces Sonic and Tails as the lead protagonists. Kirby can inhale monitors and most enemies but cannot copy their abilities. Lives function as health points and the only way to obtain them is grabbing every 50+ Rings, Checkpoints/Lampposts, Randomized 1Up Monitors, or Score every 50000+ points. The hack also features 4 difficulty modes. Hidden Palace is restored but only as a 1 Act Zone for Kirby, located somewhere in Mystic Cave Act 2.

Knuckles in Sonic the Hedgehog is a fan-made ROM of the game Sonic the Hedgehog for the Sega Mega Drive/Genesis, featuring the character Knuckles the Echidna in place of Sonic the Hedgehog, the game's usual protagonist. The history of the game begins with the release of the Mega Drive game Sonic & Knuckles. The unique cartridge featured "Lock-On Technology" and allowed players that also owned the game Sonic the Hedgehog 2 to link the two together and play the game through as Knuckles instead of Sonic. However, partly because of a poorly matching colour palette, no such feature was included in the first Sonic game (instead, attaching Sonic 1 to the Sonic & Knuckles cartridge unlocked the full version of Blue Sphere). In the ROM hacking community, creating a patch that allowed the gamer to play as Knuckles in Sonic the Hedgehog was considered the "Holy Grail of ROM Hacking." On September 1, 2005, Stealth created a hack that allowed a player to do just that. His hack was called Knuckles the Echidna in Sonic the Hedgehog (Knuckles in Sonic 1, or S1K for short) Knuckles in Sonic 1 one gives Knuckles all the moves he has in Sonic and Knuckles, including gliding, wall climbing, and the spin dash. Not only that, Knuckles can transform into his Super form once he obtains all the emeralds (a cheat must first be enabled).

Metal Sonic Hyperdrive is a heavy modification of Sonic the Hedgehog by Darkon360/GothicReaper/LoneDevil for the Sega Genesis. with brand new Zones, New Music, Extra playable characters, and Modes. Starting Metal Sonic, taking Sonic's role as the main protagonist to stop Dr'Robotnik's greatest inventions yet. Also starting special guests such as Kirby, and Somari.

Metal Sonic in Sonic 3 & Knuckles is a hack of Sonic the Hedgehog 3 & Knuckles. It was created by Darkon360/GothicReaper/LoneDevil. Metal Sonic is playable, complete with additional special moves.

Metal Sonic in Sonic the Hedgehog 2 is a hack of Sonic the Hedgehog 2 created by Darkon360/GothicReaper/LoneDevil. It stars Metal Sonic as the playable character instead of Sonic the Hedgehog. The hack comes with 3 different playstyles for Metal Sonic.

Metal Sonic Rebooted is a complete heavy modification of Sonic the Hedgehog 2 by Lone Devil for the Sega Genesis. it features an extensive amount of new art, layouts, mechanics, music, and features that in total creates a different experience.StoryDr'Robotnik has built an advanced army of badniks to search for the Chaos Emeralds, and it's up to Metal Sonic to find the emeralds before them by destroying everything in his way to show Robotnik he shouldn't be replaced.CreditsKCEXE - Music and SFX ports from various Genesis/Megadrive gamesEduardo Knuckles - Music for Magma FactoryClownacy - Sonic 2 Clone Driver v2Dark Sonic - Hardware Testing for v1.1

Mighty the Armadillo in Sonic the Hedgehog (aka Mighty in Sonic 1) is a hack of Sonic 1 by E-122-Psi, starring Mighty as the playable character instead of Sonic the Hedgehog. The game is modified to use Mighty's sprites in place of Sonic's, along with several modifications to the player's stats and abilities.