7. Loki's Pose
When Thor was talking to who he thought was Odin at the very end of the movie, the king of Asgard - who normally sits so regally and in such a smart, uniform manner - seemed to be slouched and posing very nonchalantly and it was soon revealed that Thor had actually been talking to Loki, who was using his powers of illusion to make Thor think he was talking to his father. The pose in question is a nod to the comic books, where Loki is often seen sitting in such a way (see below for an example of such a pose).
The eagle-eyed members of the audience would instantly have been able to tell that Thor was talking to Loki - even when Sir Anthony Hopkins was on screen and not Tom Hiddleston - from the pose alone.