Chris Hemsworth grew out his hair for over a year to have more authentic long hair, rather than use a wig, like he had to do in Thần Sấm Thor (2011).
The prologue was filmed in a blend of live-action and CGI, as the Asgardian/Dark Elf costumes were too constrictive in which to fight effectively and convincingly. There are only three characters played by human actors in the entire scene, Malekith, Kurse, and Bor. All other characters are CGI.
(at around 1h 23 mins) Chris Hemsworth improvised hanging Mjölnir (his Hammer) on a coat hook in a polite manner, after playing with it between takes.
This is the last movie written by Don Payne (who also wrote Thần Sấm Thor (2011)). He died from bone cancer before this movie was released.
(at around 1h 5 mins) Thor accidentally destroys a statue of his grandfather Bor, and Loki wisecracks that he killed him. In the Marvel comics, Thor ended up killing his grandfather as part of a deception by Loki.
Stan Lee: (at around 52 mins) As the man who asks Dr. Erik Selvig (Stellan Skarsgård) for his shoe back, when Dr. Selvig is in the mental ward explaining the Convergence theory.