Well, it's not Rifts, but I ran a game where a symbiant-"infused" (on his face with it's "tail" down his throat) were-bear, a gnome wizard, a halfling bard, and a reincarnated succubus cowgirl accidently-on-purpose traveled 5000 years into the future in a Van DeLorean. They had to work to get the plutonium they needed to get back to their own time, and the only way to do that in a reasonable time frame was to go hunting for ancient alien artifacts.
They used the Van DeLorean as collateral to acquire a ship, the "Lavender Phallus" (pic here and here, which belonged to a now missing bounty hunter. They got lost in space, fought a "God of Rock" (musically and geologically), and turned a prison into a brewery. They discovered the Loc-Nar, and continually tried to use it (despite it being very obviously a dumb idea). One time it turned the bard into the embodiment of Death Metal, literally melting people's faces off until the succubus (immune to its effect by virtue of her metal status as a demon) stopped him. The wizard tried to use it and became a megalomaniacal genius, who started warping space and time to take over the universe (only the true, tender love of the were-bear combined with the soothing music of the bard allowed him to reconnect with "humanity").
Finally they found a quest that would reward them the plutonium they needed. An evil accountant, Bob, had taken over the central systems by filing the appropriate paperwork, and no one could defeat his incredible use of red-tape. The only way to stop him was to offer him a job working for B.R.A.I.N.S. (Beings Required for the Astrogation Interconnecting Near Systems), the only known job that can occupy evil geniuses (other members of BRAINS include: TX50000, an ultra powerful artificial intelligence; XCLILIOPPX, an interdimensional octopus with a million minds; Madam Zora, a powerful psychic and medium whose predictions are 92.3% accurate; and Dolphin Pod 37, a pod of dolphins who think astrogation is a game). Unfortunately, no one in the Near Systems could get close enough to Bob to make him the offer, as they would be bound by law and bureaucracy which Bob controlled. So the PCs were hired, and they saved the universe, getting their plutonium as a reward.
When they returned for their Van DeLorean, the junk dealer tried to backstab them, wanting the time machine for himself. However, the were-bear ate him, and they went back to their own time, and the were-bear was reunited with his were-wyvern son.
