If you are a Crispin Glover fan, you must see this. If you are a Sean Penn fan, you must see this. If you are a movie fan in general, you must see this. If you have no idea who Crispin Glover is and you have no idea who Sean Penn is, this film will probably still have a lot of value, but the more work you've previously seen by Crispin or Sean, the better.
This movie is so funny, but it is also pure genius. There is nothing that I know of that resembles this film. It is its own genre. I doubt that anything like it will ever be made again. I cannot say anything more about exactly why without partially spoiling it, and some of the other reviews here have already done a good job at doing that.
In response to any of the reviewers here that gave it a bad review, I ask that you view the film again. In reality, there is no point at which this film could fairly be called "boring." This is possibly the funniest, most entertaining, and least boring film ever made. And it only gets better with age and repeated viewings. A timeless classic that, unfortunately, very few will be able to claim to have seen.
Beaver Trilogy is the brilliant work of director Trent Harris, also responsible for the amazing Rubin and Ed, which Crispin Glover also stars in.
Unfortunately, copies of this film are rare and hard to find. I managed to find a VHS version after some diligent searching though, and there are a couple of ways to find it that I know of. But I really wish someone would put this onto a DVD.