"Who Goes There?" 
Written by John W. Campbell, Jr.
The Thing 
Written by Bill Lancaster
Directed by John Carpenter
If I've learned anything from The Thing, it's that being a scientist totally kicks ass! You get to hang out in the Antarctic with dogs and helicopters. You get a private arsenal of guns and flamethrowers. You get a pinball machine and computer chess. You get lots of booze and some weed. And you get to rock out to old-school Stevie Wonder ("Superstitious" to be exact). The only problem is that you could become infected by a malevolent amorphous extraterrestrial. And then Kurt Russell would have to set you on fire. (Which, as deaths go, would still be one of the top 10 most awesome ways to check out.)
Upon its initial release, The Thing met with considerable critical derision and audience disgust. Bob Bottin's literally eye-popping SFX work was just too much for early 80s audiences to digest (pun intended). Many critics grumbled that Carpenter had merely remade a classic, 1951's The Thing From Another World, and diluted it with gore and slime. Eventually, The Thing would find a second life on home video; it is now recognized as a modern classic of science fiction/horror and a benchmark in the history of special effects. However, it is still not uncommon to see the film referred to simply as a remake, a notion which will serve as the focus of this post.
Both The Thing From Another World and The Thing are based on John W. Campbell, Jr.'s short story "Who Goes There?". The first film is derived from the first half of the story, the latter from the second half. The notion that the Antarctic scientists discover the Thing's ship and bring the alien into their camp is used in the 1951 adaptation; in Carpenter's Thing the xenomorph uses the body of a husky to infiltrate the camp. But the 1951 monster is no shape-shifter. It's actually an intelligent space vegetable which vaguely resembles Karloff's Frankenstein's monster (and is played by a pre-Gunsmoke James Arness). Campbell's constantly mutating alien is reintroduced in the '82 Thing, and along with it comes a wave of paranoia unthinkable when trying to fry a killer space carrot.
Anyone could be the Thing. It could be Kurt Russell. It could be the black guy who does the voice-over work for US Navy commercials. It could be the farmer from Babe, the guy who married the mom in Six Feet Under. It could be Wilford Brimley. (Yes, the Quaker Oats guy.) And there's no way to know who's a monster until they explode into a slimy, writhing mass of tentacles and teeth. Campbell's Thing-infected scientists transform, but the author never dwells over their metamorphoses. Carpenter on the other hand gives us every gory detail.
The major discrepancy between short story and movie is the ending. Campbell finishes his tale with an improbably happy finale. He sets up the possibility for some ambiguity (and thus some lasting dramatic tension), and then off-handedly dismisses it with a sentence. Don't worry, all that messy "Thing" nonsense has been completely tidied up. Oh, and we might have just discovered the secret to unlimited energy and anti-gravity. Carpenter's ending is much darker. I won't spoil it here; just don't expect a tidy, rosy conclusion (not that you would based on the preceding hour and a half).
If you've got the stomach for it, you really need to see The Thing. It's a masterpiece, a rare film which deftly balances extreme gore with genuine creeping terror. For a fun follow-up, check out the song "The Thing" by the group Engorged (www.myspace.com/engorged) on their seminal Where Monsters Dwell album. It's a five minute deaththrash summary of the plot complete with samples from both Thing films.
And remember....KEEP WATCHING THE SKIES!!!