The ThingFor the Marvel Comics superhero see Ben Grimm
The Thing is an extraterrestrial monster in the movie The Thing From Another World (1951) by Howard Hawks, remade by John Carpenter as The Thing (1982); the movies are based on a novella called "Who Goes There" (1937) by John W. Campbell. The first film has little in common with the original story except for the finding of the alien vessel and the thawing out of its occupant. The second version, with its grisly special effects, is a fairly faithful rendering, even to the method used to find which are the hidden aliens.
The Carpenter film is notable for improving on the Campbell story, by better distinguishing the monster from humanity in cognitive terms. Instead of being merely a material creature, the monster is shown as a principle of nature and thus knowable by man. The solution to the question of human identity presented, thus becomes an ironic device, showing the audience itself its own identity as humans, should they have the wit to detect it.