Gremlin Nova is a blueGremlin who's caged in Tomorrow Square in Tomorrow City. He's on a platform that's only accessible via the Rocket Ride. Mickey should activate the Rocket Ride after going up the secret path he would normally use to get on the trams. After the ride is fixed, jump on a rocket and ride it up to Nova. After he's free, he does two things for Mickey: One is restoring power to the People Mover, saving him from doing the job himself. The second thing (that he can't do himself) is completely removing the trams from the track. This makes the road to the exit a lot safer, leaving the electricity as the only thing Mickey has to worry about.
Nova's name is a reference to a nova, a nuclear explosion that occurs when a dwarf star ignites due to accretion of hydrogen. This space name is understandable, since this Gremlin works in an outer space-afflicted section of Wasteland.