I doubt this clip is all that obscure. The statistics for it says it's been viewed a quarter of a million times. That's a lot for YouTube. It was one of those things that appeared when I was looking for something else. It's funny. But it's also instructive.
The reason it's funny is not simple. The reason it's funny is because it's not a joke.
Jokes are not really funny. Jokes are a sort of catalog of shared foolishness. They're a kind of checklist. The laughter at the end is either perfunctory, a roar of a mob with a shared worldview that generally approaches received-knowledge-psychosis, or a nervous reaction to the mildly disconcerting.
Perhaps I shouldn't be using the word "funny" anyway. It's "humor" we're after, and that video has it. Why? Because it's a story told in a humorous way, not a joke.
It's much harder to tell a story in a humorous way than to tell a joke. Look at a young Kevin Spacey do two dead-on imitations in that thing, and the other fellow doing Richard Dreyfuss, and picture the amount of time spent watching the subject of the mimicry and then standing in front of the mirror to get it right. It would have been a lot easier to write a sentence or two that relied on R2D2's height in relation to C3PO's crotch and be done with it. But you'd just hear that once, titter a little --maybe-- and then the thing is dead for long enough to forget the punch line.
There's a kind of wonder you get from watching the distillation of a handful of absurdities into a little shot of humor, that gives the finished product a kind of half-life a joke never has. Until the people and the subject matter become obscure, you could watch that over and over.
Tell a story in a humorous way. Skip the joke.
(Update: The always culturally astute commenter Ruth Anne has pointed out the "other fellow" is Darrell Hammond.)