Ristar’s origins date back to the brainstorming sessions of Sonic the Hedgehog for the Genesis. A rabbit that could throw and grab objects was amongst the several ideas for Sonic. Sonic Team settled for a platforming game with an emphasis on speed for their blue hedgehog, but did not discard the rabbit idea from their minds.
The game was named Feel in older builds, and the character had a distinct appearance. The protagonist had shoes similar to Sonic’s, and, although still sporting an orb shape, had two horns that resembled rabbit ears. Oddly enough, an enemy in the final is a rabbit that attacks with its ears, and a valid cheat is “FEEL”. Four prototypes (in the beta phase) were leaked by the Hidden Palace site, but are close to completion.
A specific prototype is named Dexstar, proving that several title changes occurred after the Feel prototypes. The enigmatic “STAR” cheat, exclusive to the Japanese retail copy, makes the game ask about a player’s wish and displays a shooting star. It does not seemingly change the game and is likely an easter egg of sorts. When it is inputted in one prototype it proclaims that “Star Star Mode” has been enabled, but it changes nothing in the game. This means the “STAR” cheat’s effect was eliminated earlier in development (or replaced by another code) and is only referenced as an easter egg.
Some beta differences can be found at Ristar Cluster, take note that it also discusses the Game Gear version of the game when my analysis is focusing on the Genesis/Mega Drive one: http://ristar-cluster.info/php-pages/proto.htm
Localization alterations in both Genesis/Mega Drive games: http://ristar-cluster.info/php-pages/jpn-vs-usa.htm
STAR cheat: http://www.x-cult.org/games/117/Ristar/631/Star_Mode/