He takes the form of an orb of blue and white light, similar to Tikal's form of a floating red and white sphere of light. Because Uhu is not under the control of a master, he serves as Sonic's opponent for certain racing challenges, once per world. He is said to be famous for his speed, which appears to explain why he challenges Sonic in the first place.
When Sonic faces Uhu, a distance meter appears in the top-right corner of the screen, showing the difference in distance between the two in meters. If Sonic falls too far behind, it turns red. When they're close, it becomes the regular text color. And when Sonic is ahead, it turns green. While Sonic cannot fail the mission by dying, it does cost him significant time, allowing Uhu to catch up. It appears that Uhu's AI system is set to the standard path that the player would normally take, no shortcuts or Speed Breaks.
Uhu is also able to bounce on enemies, but not destroy them. This is so Sonic will be able to use the Homing Attack on the enemies to continue on.