It takes a certain kind of taste really enjoy this movie. But if you're like me and you love a good, narmy B-movie, you'd be hard pressed to do better than Killer Klowns From Outer Space.
This movie knows full well what it is, so rather than try to play it seriously or lampshade it, they simply put on the closest thing to a straight face they can muster and play it through. And it is FUN.
The characters are reasonably likable. No one I would name the movie after, but they move the story along and I do genuinely care about what happens to them. While the real focus of the film is the titular horde of alien clowns, the protagonists do a fairly good job of building suspense and rising action as they work against the ever growing threat.
The clowns themselves are the best part, however. There are none of your traditional "clowns are creepy" lines, but rather, the irony of a monster clown is played in full force. These guys are chaotic! They're not an invasion force by any means. They just want some nice, cotton candy-wrapped humans for the road, and they enjoy themselves while rounding up their munchies. They're borderline omnipotent with the sheer array of bizarre circus-themed powers and technology they wield, but they do little more than goof off while basically out shopping. They're a casual, creepy, astoundingly fun antagonist.
The movie, had it been made ten years later, would probably be called a George Lucas Throwback. As it is, it's a wonderfully enjoyable romp that doesn't even try to take itself seriously, but puts on a straight face anyway just for fun.