Finding Nemo is a platformer for the Sega Mega Drive made by Glorysun, and a simple graphical hack of James Pond, originally developed by Vectordean Ltd, Millenium Interactive and Electronic Arts.
Knuckles the Echidna in Sonic the Hedgehog was a planned add-on for Sonic the Hedgehog which allowed you to play as Knuckles by attaching the cartridge to Sonic & Knuckles. The game was only previewed once in volume 44 of SEGA Megazone.
The game was later replaced by Blue Sphere in the final release of Sonic & Knuckles.
Beethoven's 2nd: The Quest for Pups is an unreleased action game for the Sega Mega Drive based on the film, Beethoven's 2nd. An entirely different Beethoven's 2nd game was released around the same period for the Super NES. It was featured at Winter CES 1993.
A prototype of the Mega Drive version was released by Hidden Palace on January 1, 2022.
Mickey Mania 2 was a planned sequel to Mickey Mania: The Timeless Adventures of Mickey Mouse, set to arrive on the Sega Mega Drive. The game was not officially announced, but its existence was revealed by Jon Burton, co-founder of Traveller's Tales.
The game would have played similarly to the first, though would have featured stages based on different Mickey Mouse cartoons as well as including new mechanics. It was cancelled by Traveller's Tales in favour of the console version of Toy Story, though an early prototype is known to exist.
Footage of the prototype shows a wild west stage and a ship stage loosely based on the 1934 cartoons, Two-Gun Mickey and Shanghaied, respectively. The latter stage originally featured a scrolling floor and a first-person stage that jokingly used a placeholder HUD to parody Doom - these features would be repurposed for Toy Story.
Queen of Poker Club is an adult, unlicensed poker game developed by Thin Chen Enterprise and published by Sachen, and released exclusively in Taiwan sometime in the 1990s.
Sonic the Hedgehog 3 Limited Edition was going to be a compilation of Sonic the Hedgehog 3 and Sonic & Knuckles for the Sega Mega Drive. This would be similar to what happens when locking the two games together with Sonic & Knuckles' Lock-On Technology. It would essentially be Sonic the Hedgehog 3 & Knuckles, but it would have been contained in a single cartridge and thus probably would have had a cheaper price. It is unknown whether it would have had a port allowing for Lock-On Technology so compatibility with other cartridges is also unknown.