Revealing mistake: The Thing takes a swing at the captain after the captain opens the door. As the Thing swings his arm, he takes out a chunk of wood out of the door. If you step through the frames on the DVD, you can see the wood leaving the door a full second after the Thing has hit it. A small explosive charge that was not in sync with the actor. You can also see the outline of where the wood comes off before he swings his arm. And one more thing, his arm does not touch the door or even comes close to where the wood comes off - a safety precaution I presume. (00:57:33)
Suggested correction: It is not a full second delay. It is four frames which translates to 1/6 of a second. Everything described in this entry is only visible if you step through frame by frame which invalidates the mistake.
Continuity mistake: When Raymond Burr emerges from the door at the beginning of the movie, in the first shot he is in the background while Mrs. Van Gelder is dancing. Notice that the decoration to the left of the door frame casts no shadow, but in the next shot the ambient lights have changed so much that now the hanging sculpture projects a huge one. (00:02:50)