A Gnome Named Gnorm

A Gnome Named Gnorm (also known in some markets as Upworld) is a 1990 fantasy buddy comedy film directed by Stan Winston and written by Pen Densham and John Watson. The film stars Anthony Michael Hall, Jerry Orbach and Claudia Christian, and is about a Los Angeles police detective who teams up with a gnome to solve a murder.
Plot.
Gnorm is just an average gnome (a tunneler) who lives underground, but he wants to impress a lady gnome by doing something heroic. So he takes the lumen, a stone that must be brought to the surface (called Upworld by the gnomes) to be exposed to the sun to recharge it. When he gets to the surface, he witnesses a murder and the killer ends up with the lumen. Detective Casey (Hall), who was working a sting operation with the murdered man, is blamed for botching the sting, and the man's death. Wanting to catch the killer to clear his name, he teams up with Gnorm, whom he accidentally discovers. He is going to need his partner Samantha's (Christian) help, but she thinks he is a nut. See, no one else knows about Gnorm.