Even though it's incredibly hard to believe and goes against sound Sun rises in the east and sets in the west logic, Chris Hemsworth (and to a lesser extent Thor) is not a perfect being that doesn't make goofy mistakes. This gag reel proves he's human after all! Just like us! And sometimes moments get awkward and sometime he falls and sometime he flubs up. But damn, he makes it look so fun to screw up.
Seriously, he's so good at messing up that even when he does make a mistake, he makes it so entertaining that I had just as much watching this gag reel of Thor: The Dark World (posted by Hiddleston-Daily) as I did watching the actual movie.