Trivia: Much of the ending was reshot, including a scene where the alien pilots within the spaceship were witnessed by Kate Lloyd dangling from some sort of tubes; the body of one was replaced post-production by an odd Tetris-like display.
Trivia: The showdown with the Dr. Sander Halvorson-thing was done as a disappointing rush job when the ending was hastily replaced - Kate Lloyd was meant to encounter the spaceship's pilots and a whole other confrontation was devised, along with Dr. Halvorson being dead.
Trivia: Early script ideas for the plot included having MacReady and Childs rescued but frostbitten and then the horrid truth about one (or both) revealed, or having MacReady's helicopter pilot brother come by the camp and discover the disaster there. Director Matthijs van Heijningen Jr. wanted to remind the audience of MacReady with the character of helicopter pilot Sam Carter (played by Joel Edgerton).
Suggested correction: It is also established in this film that the creature cannot perfectly imitate inorganic materials; the tooth fillings, metal plate, etc. Kate knows that Carter is The Thing and asks him a trick question about his earring to confirm it. The fact that The Thing reaches for the wrong ear means that it didn't know where the earring really was because it cannot perfectly imitate inorganic materials. There is no mistake here.
THGhost
The mistake has nothing to do with The Thing not being able to imitate inorganic material. The mistake is The Thing has all the memories and thus should know which ear was pierced based on these memories.
Bishop73
This goes with my theory that he was actually human because he didn't try to assimilate her when they we're alone and far away from people, and he didn't change when he was threatened and accused which was backed by (potentially false if the theory is correct) evidence which would make it defend itself.
You're obviously wrong here. The Thing imitates the human perfectly including the memory and I'm pretty sure that if you only have one ear pierced you'd know which one is it, therefore the imitation would know.