The 1999 science fiction comedy Galaxy Quest is a classic in both genres. Aliens from a faraway galaxy come to earth and approach the cast of a science fiction television series, believing them to be the earth's real heroes. These aliens are Thermians, whose true form is like that of an octopus. They were really funny, but their very existence brings up questions of how intelligent life on other planets may present themselves. The Thermians made themselves look and sound like Earthlings, but as they come from a different culture, they don't quite get it right. All their research on our planet was done through television signals. The result was a group of alien space travelers who spanned the uncanny valley.
How actors hit the sweet spot in this uncanny valley was quite a story. The Thermians weren't fleshed out in the original story, and the actors improvised as they went along. Not only did they have to come up with their entire nature, they had to learn to do it in lockstep with each other. How does one become an alien who wants to seem human but can't? Thermians ended up being not only funny, but also believable and sympathetic. -via Kottke