Looking for short films again, but this time I'm thinking of something a bit longer. What's a great sci-fi film, about 15-to-30 minutes long, that has a clear message and deep meaning?

I'm thinking of doing a quick project with my high school students involving a short film - and with that in mind, the films shouldn't have any nudity and as little graphic content as possible.

We're going to be reading science fiction next week, so it should probably be something in that vein. As for tone - funny, sad, introspective - it's all good.

Any ideas?

(For the record, I've already used I'm Here for a different assignment.)