Sonic Jr. (lost build of unreleased Sega Pico game; existence unconfirmed; 1994)
From The Lost Media Wiki
Sonic Jr. was to be a Sonic the Hedgehog title for the SEGA Pico, an educational console. The game was announced at the same time as the release of Ecco Jr., and the game would have likely been similar in concept. Whether the eponymous Sonic Jr. was a new character or simply a younger version of Sonic is unknown, or even if the game made it off the drawing board. In the end, Sega instead released Tails and the Music Maker and Sonic the Hedgehog's Gameworld.