Fanfiction: Writings about existing franchises

You forgot the far future sci-fi version where they wake up on the planet XN-254b with no fucking clue about how they just achieved the trip in one night when it normally takes several years, even at superluminal speeds. And the random animal is a perfectly normal earth gerbil. The gerbil must be protected because everything on XN-254b wants to eat it, including the alien residents. Also, one of the guys appears to be pregnant and needs to get an alien abortion before getting back to Earth for his wedding.

(As a screenwriter, I'm tempted to actually do this. Not as fanfic, but as a real, marketable screenplay. "The Hangover, but in _________" comparison would probably play pretty well with film execs, and there's not actually any major IP hurdles to being able to do this. You couldn't call it 'the hangover' because that'll be trademarked, but as long as you give it a different title, it should fly. You're not using anything copyrightable here. Only real issue is that these knock-off versions will necessarily have significantly higher production costs. Period pieces or sci-fi pieces are always going to have more expensive and elaborate sets, props, and costumes. You could do it in increasingly remote, exotic contemporary locations, but then that also increases costs due to having to get the entire film crew to that exotic location.)