Sonic 3D: No Flickies is a hack of Sonic 3D: Flickies' Island made by Sik. The game remains mostly unchanged; however, the Flicky collection system (part of the core gameplay of the original game) has been removed, allowing the player to complete the levels without needing to collect all the flickies in the level to advance. This makes it much more similar to traditional Sonic games, where the goal is to simply make it to the end of the level without dying.This hack was later built upon further in the hack, Super Sonic in Sonic 3D, which was also created by Sik.

Sonic & Knuckles (ソニック&ナックルズ Sonikku to Nakkuruzu?) is a 1994 platform video game in the Sonic the Hedgehog series for the Sega Genesis. It was developed in the United States at Sega Technical Institute by members of Sonic Team, and was published by Sega worldwide on October 18, 1994.In addition to being a standalone game, through a system dubbed "lock-on technology," Sonic & Knuckles acts as an expansion pack to both Sonic the Hedgehog 2 and Sonic the Hedgehog 3, the latter with which it was developed in tandem.

Sonic the Hedgehog 3 and Sonic & Knuckles were originally to be released as one game,[4] but due to time and financial constraints, it was later split into two separate games. However, Sonic & Knuckles contained "Lock-on Technology", where the Sonic & Knuckles cartridge would be put in the Sega Genesis system, and then another game could be placed onto the top of the Sonic & Knuckles cartridge itself.[4] When Sonic 3 is used in this manner, it enables the player to play through both games as one, titled in-game as Sonic 3 & Knuckles. This features several additions to the games not available otherwise, such as small alterations to the levels, and being able to play through Sonic 3 levels as Knuckles, or Sonic & Knuckles levels as Tails, and the ability to save progress in all of the game's levels.Additionally, this was the only way to collect Super Emeralds, which are earned by accessing Special Stages in the Sonic & Knuckles levels after collecting all seven Chaos Emeralds from Sonic 3. When all Super Emeralds have been collected, Sonic, Knuckles and Tails can transform into Hyper Sonic, Hyper Knuckles and Super Tails respectively, each with unique abilities.

Sonic And The Mystic Gems (previously known as Sonic 1 Harder Levels) is a hack made by Eduardo Knuckles and his team Harder Project of Sonic the Hedgehog on the Sega Mega Drive. It began in 2005 with the simple purpose of being a generic Sonic 1 for Sega Genesis with increase difficulty and revamped versions of the original levels. But now, it's going to present a completely new gaming experience with a new style of level layouts full of paths everywhere among new enemies, new objects, new character abilities, new menus, completely different styles of the Sonic 1 special stages and much more!Credits and Special ThanksMistergambit for his Spring Yard Zone and Labyrinth Zone level art used in the game.Tweaker for his information regarding music importing, bug fixes and the speedcap removal.HPZMan for the new sound driver instruments and the dynamic tile-set system.Selbi for some new exclusive ASM things and improvements.Master3k for sending and fixing some music.nineko for creating the xm3smps tool which was essential for the creation of some songs. Special credits to him for the different songs per act system used.SCAA for their art.Puto for his tutorial to add Spin Dash.FraGag for his tutorial to fix the spike bug.SonicVaan for beta testing.HCKTROX for the lead programming and bug fixing.GenesisFan64 for the save screen menu, for some fixes related to the fade-out and others.MarkeyJester for lots of important code and a whole load of others.Irixion for beta testing.PsychoSk8r for his the dynamic palettes tutorial.Esrael for fixing essential things in the new sound driver.Prilix Bõkun for bug searching and beta-testingEstlib for various art stuff related to levels and for additional help with creation of gimmicks and objectsDJ. Joker27 for his very big importance in specific level and misc musicMighty Arnold for additional support with beta-testing and level layout designKenny0989 for additional support in the music department Special credits to Harder Project's Team by all the useful exclusively things used in the project.