It's the Battle of the Sexes as Savage Planet Women Attack Female Space Invaders. Women Of The Prehistoric Planet:
A spaceship crash-lands on the third planet of a distant solar system, killing all hands except for a young boy named Tang. The rescue ship arrives some 20 years later. One of the crew, a girl named Linda, meets Tang and falls in love with him. The rescue team is attacked by the native life of the planet and many of them are killed off. When the ship leaves, Linda decides to stay with Tang.
I always forget that this is a season one(1) episode. The quality of the entire episode is something I expect of season four(4) or five(5). Anyways, this is a great movie with a horribly low budget and a slight predictability in the "twist" at the end... yet it's still one of the better movies they've ever riffed. It really just reminds me of a better episode of the Star Trek original series. Of course, that's not saying too much, but still, I actually really like this movie.
As for jokes, they are all great... The movie's "comic relief" provides some great riff fodder, as does the voice of the captain. The host segments are wonderful, the opening segment providing us with the show's first real original song. The last segment has them reading a letter from the winner of a competition from a later episode. I am sure this has to do with rights issues and television networks' typical ability of reordering episodes.
Anyways, yeah... great episode. That's all.