AnimationThe idle animation of Ristar is unique for each planet in the game.
DevelopmentThe arm moves of Ristar were originally intended for a Sonic the Hedgehog game.
Regional differencesThere was a lot of changes between regions for Ristar. For example the Ice Planet's (Western's Freon or Japan's Elykiki) boss was a robotic cat. In the Western versions, it was an ice monster. Other changes were made like the story of the Legendary Hero was not in the Japanese version, Ristar was born from the wishes of help from the Elder on Flora/Neer not from the son of a giant handed hero.
Also, the PAL Sega Mega Drive/Genesis has a higher resolution than the NTSC system. Most games just add borders to compensate for the higher resolution. But Ristar is one of the few games that actually takes advantage of this resolution and uses the full screen.
Information also contributed by ケヴィン, djbrayster, and MegamanX64