Sonic UltraSaturn

After Knuckles and his friends defeated Dr. Robotnik, peace held for a few months. Now Robotnik is back, quietly gathering the pieces of his destroyed Metal Sonic Kai and heading toward Saturn's Moon — a satellite that appears for only three days every century. When a giant hologram of Robotnik's face announces that Mobius will be destroyed by crashing the moon into it in an event he calls Fat Tuesday, Sonic, Tails, and Knuckles race to stop him.