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.
The idle animation of Ristar is unique for each planet in the game.
There was a lot of changes between Regions for Ristar. Example in Japan the Ice Planet's (Western's Freon or Japan's Elykiki) Boss was a Robotic Cat. In the Western versions it was a Ice Monster!
Other odd changes were made like the story of the Legendary Hero was not in the Japanese version, Ristar was born from the wish of help from the Elder on Flora/Neer not the Son of an Giant handed Hero!
The arm moves of Ristar were originally intend for a Sonic the Hedgehog game.