Briefly, the FF adventure was based on something james_nicoll mentioned, the Bone Wars between rival paleontologists in the 19th century. I changed this to the 23rd century and set it on the (habitable) Jupiter of A Struggle for Empire.
One group (the adventurers) were looking for evidence of Panspermia and their rivals convergent evolution in explaining how multiple worlds had human inhabitants. Things were of course complicated by the ongoing interstellar war and siege of Jupiter, which meant that after the expedition's leader was killed the adventurers were isolated 80K miles from civilisation, their only transport a slow antigravity yacht with no spacegoing capabilities, and couldn't risk calling for help, since a flying torpedo can really ruin your day. I was expecting them to make their way back, fighting off native hordes, monsters, and eventually the CE enthusiasts.
What I hadn't anticipated was that the adventurers (Most notably General Malcolm Reynolds and his batman Sgt. Fred T. Jayne, both retired and annoyed because they were side-lined in the war) would decide that it was their patriotic duty to to try to strike a blow against the Sirian hordes, and lure an enemy ship into an explosive trap in a canyon... which they had just prepared and baited (with a radio message) when the rival paleontologists turned up, guns blazing.
This led to a gun battle and assorted heroics, abject defeat of the Convergent Evolution enthusiasts, and a quick retreat to cover leaving the CE yacht as bait for the Sirians.
When a Sirian destroyer duly arrived the adventurers set off their trap which duly brought a cliff down - totally missing the destroyer, but crushing the CE yacht! This would have been a bit of a problem, but fortunately the yacht's fuel tanks exploded, and the blast blew a couple of boulders through the destroyer's hull. Our heroes quickly followed up with their cannon and Maxim guns, causing more explosions in the enemy ship which started to sink towards the canyon floor. Realising the size of explosion that was likely if the destroyer's fuel tanks or magazine detonated, the adventurers put pedal to the metal (inadvertently abandoning the natives who had helped prepare the trap) and headed off at emergency speed, and thus survived the fairly large explosion that followed. Needless to say the native bearers, CE enthusiasts and Sirians weren't so lucky...
Anyway, it wasn't exactly what I'd anticipated, and I had to do a LOT of improvising, but it worked pretty well.
The Fanfic adventure didn't go as well,mostly I think because the players ignored my request that they put together a plausible team of crime-fighting park rangers and instead went with a group that made no sense; Gaius Baltar, Gaius Julius Caesar, JD Dorian (Scrubs), Napoleon Solo, Christian Bale (studying the park ranger service for his next movie and prone to method act to a ridiculous extent), and Fox Mulder. They started off by killing a moose (which wasn't exactly in my game plan) and Caesar quickly moved on to sacrificing a cub scout to appease Vulcan, god of the volcano under the park. From there it went downhill, and I had to make the actual plot way too obvious to keep them in the game. This eventually led to JD encountering an Austin Powers femmebot and getting badly shot, and Fox and Bale getting mind controlled and killing most of the rest. They never got anywhere near the actual villain, Yogi Bear, who had faked his own death and was using his fiendish hyper-intelligence and mind control powers (think Gorilla Grodd) to plot the destruction of the park, detonation of the Jellystone super-volcano with the eventual goal of arming his bear hordes and taking over. It was fun, but it wasn't a very coherent game, and I think I screwed up by giving the players too much freedom without immediate consequences. Next time I think I'll give them better guidelines on character choice etc., and make it clear that what they come up to has to be something that would work if it was a TV show, we'll see if that makes a difference.
Anyway, two interesting but exhausting sessions - I stayed on for the auction (which raised £1460 for charity) but couldn't afford anything I actually wanted, then decided I'd skip going for a meal or to the pub and went home and got an early night. Next time I really need to pace myself a bit better...