I've seen it many times, and been tempted, but something always kept me away from UHF (1989). On paper, it looks like a must-see: Weird Al Yankovic doing Kentucky-Fried Movie style riffs on TV. But there was also something sketchy about it that made me want to keep it at arms length. I finally succumbed and I can give it my heartiest qualified recommendation.
Al is an underemployed loser who keeps getting fired because he is a daydreamer - dreaming he is Indiana Jones in a parody of the rolling boulder scene while he lets the fries burn at his fast food job, for ex. This is a good example of the strengths and weaknesses of the movie. The parody is cute, but a little predictable. Also, in some parts, it's just Weird Al doing the scene without any jokes - it's funny because it's Al. This is very much YMMV.
His doting aunt gets him a job managing a failing UHF station. This allows for a few more parodies, including a cover of the Ballad of Jed Clampett done in the style of the Money for Nothing video. Note: This is the ONLY Weird Al song parody in the movie. Again, strength and weakness.
When he hires dim-witted janitor Michael Richards to be his kiddy show host, the weirdness leads to ratings, and the station starts to make money. This isn't quite believable, but is kind of funny. Also, Fran Drescher as the receptionist who wants to be a news reporter with her cameraman Billy Barty (fond of low-level shots) are likewise smile-worthy but not laugh-out loud.
Still, lots of comic talent (I'm leaving out Gedde Watanabe and Victoria Jackson), just not a lot for them to do. I liked the parody stuff, but there wasn't enough of it. It also tended to jump to the most obvious and predictable gag - but done well enough that you might not care.
So if you love Weird Al, you'll like this, at least. And there is a Dr. Demento cameo. That's worth something.