A famous fan-made ROM hack of Sonic 1 for the Sega Genesis/Mega Drive, known for vastly expanding the game (new characters, moves, physics, and original levels). It's not a simple palette swap.

Critically, the game is not without its challenges. As a ROM hack, it assumes a certain level of player competence. The level design can be unforgiving, and the increased speed means the player must react faster than in the original titles. However, this difficulty is a feature, not a bug. It caters to the hardcore fanbase that had memorized every loop and spring in the original games and craved a new challenge.

Sonic Megamix 5.0 (and its modern successor, Sonic Megamix Mania

Sonic Megamix 5.0 is an unfinished, leaked alpha build of a massive ROM hack originally intended for the Sega Mega-CD. It is famous in the fan community for its troubled development: The Leak and Cancellation

, and an expanded roster including Sonic, Mighty, Shadow, Tails, and Knuckles. Spiritual Successor

The rise of digital music platforms has transformed the way we consume and interact with music. Sonic Megamix 5.0 Online is a cutting-edge music mashup platform that allows users to create and share their own remixes of popular songs. This paper explores the features and functionalities of Sonic Megamix 5.0 Online, its impact on the music industry, and the potential benefits and challenges of using such a platform.

: Considered the last fully "stable" release for the Sega Genesis.