* AbilityOverAppearance: In the comics, Heimdall is pretty covered up, but still visibly Caucasian. For the film, however, Kenneth Branagh chose to cast very much black {{Creator/Idris Elba}}. Fan controversy over his choice led to this quote:
-->"If you have a chance to have a great actor in the part, everything else is irrelevant. "
* ActorAllusion:
** The Son of Coul asks Thor if he received his training with Special Forces. Chris Hemsworth was trained by a former Navy SEAL for his role as the god of thunder.
** [[Creator/SamuelLJackson Nick Fury]] talks about "[[Film/RevengeOfTheSith unlimited power]]".
* ActorSharedBackground: Sif is the lone female warrior in Thor's FiveManBand. Her actress Jaime Alexander had been one of few girls on her high school wrestling team.
* AwesomeDearBoy: Natalie Portman's words on accepting the role - before even being offered a script - were "Kenneth Branagh doing ''Thor'' is super weird. I've got to do it." As Jane's character was developed, Portman jumped at the chance to play a lady scientist too.
* DarkHorseCasting: The casting of Creator/ChrisHemsworth and Creator/TomHiddleston, whose most famous roles back then were bit parts at most, in the lead male roles was very unexpected at the time.
* DeletedRole: Adriana Barraza had a sizeable supporting role as the diner owner Izabella Alverez. Most of her scenes were cut and she only appears once in the final film. Kenneth Branagh sent a letter of apology to the actress.
* DeletedScene: A few were shot that reinforced the ambiguity and depth of Loki's character, most notably one where Frigga officially passes the throne to him and he seems startled that he's expected to take it.
* DyeingForYourArt
** Creator/TomHiddleston originally auditioned to play the title character and gained 20 lbs of muscle to help look the part. When it was decided he was better suited to play Thor's lean and dark brother Loki, he had to slim down and dye his (naturally blond) hair black.
** Once he was cast as Thor, Creator/ChrisHemsworth, having never worked out before, underwent six months of training with a US Navy SEAL and continued to gain so much muscle right up to filming that when he first put on his costume, it was too tight for him.
* EasterEgg: If you look really closely, you can see ComicBook/TheInfinityGauntlet in the arsenal at the start of the movie. This ends up being a CallForward to [[spoiler:''Film/{{The Avengers|2012}}'' and the Franchise/MarvelCinematicUniverse at large]].
* EnforcedMethodActing: The scene where Loki briefly tries to intervene in Thor's banishment, but is silenced by a sort of roar from Odin was "unscripted genius[...] Terrifying. Magnificent." on Anthony Hopkins' part, and Tom Hiddleston's startled, shrinking reaction was not acting.
* FakeBrit: Chris Hemsworth (Thor) is Australian, Jaimie Alexander (Sif) and Joshua Dallas (Fandral) are American. Anthony Hopkins (Odin) is Welsh.
* ICallItVera: Thor and Loki both wield named weapons: Mjölnir, the hammer, and Gungnir, Odin's spear. Clark Gregg, who plays Agent Phil Coulson, felt that he also should have a named weapon, so he decided that his Glock 17 was "Glockenspiel."
* MeanCharacterNiceActor: TomHiddleston, who plays Loki, can nail cold, calculating and manipulative like nobody's business. In real life, he comes across as very sweet, enthusiastic and clearly delighted with his job and can barely contain his glee when gushing about his costars and genuinely appreciates his fans. Stan Lee has described him as "the sweetest, nicest guy you could ever meet".
* TheOtherMarty: Stuart Townsend was cast as Fandral but replaced by Josh Dallas days before filming began.
* [[PlayingAgainstType/FilmDirecting Playing Against Type: Film Directing]]: KennethBranagh, who's better known for Shakespearean films, took a turn at directing a superhero flick. This is apparently because he was a fan of the comic as a child.
* SeparatedAtBirthCasting: Dakota Goyo and Ted Allpress who play Thor and Loki as children respectively really do resemble Chris Hemsworth and Tom Hiddleston.
* StarMakingRole: Creator/TomHiddleston was virtually unknown worldwide before playing Loki, and is now one of the online fandom's most beloved stars.
* ThrowItIn:
** Anthony Hopkins improvised his reaction to Thor's CallingTheOldManOut speech. Apparently, crew members were [[{{Tearjerker}} bursting into tears]] on the set during filming.
** Odin's terrifying and definitely unscripted growl when Loki attempts to intervene deserves a mention by itself.
* WhatCouldHaveBeen:
** '''[[Creator/BrianBlessed BRIAN BLESSED]]''' was originally slated to play Odin. Zachary Levi of Series/{{Chuck}} and Stuart Townsend had both been cast as Fandral before Josh Dallas took over. Creator/AlexanderSkarsgard was also tested for the role of Thor, which would have made for an interesting dynamic considering his dad Creator/StellanSkarsgard is playing Erik. Creator/DanielCraig, and Channing Tatum were also considered for the role of Thor. Interestingly, Levi would replaced Dallas as Fandral for ''Film/ThorTheDarkWorld''.
** Let's not forget that blue-eyed, blond-haired, 6'2", classically trained Creator/TomHiddleston originally auditioned for the role of Thor, even going so far as to put on 3.5 stone (that's 49 lbs!) of muscle for the part. He didn't get the role of Thor, but [[{{Understatement}} things turned out pretty okay for him regardless.]]
** Not only does [[Series/{{Rome}} Titus Pullo]] play Volstagg, but Kevin [=McKidd=] (AKA [[Series/{{Rome}} Lucius Vorenus]]) was originally slated to play Dr. Donald Blake before the character was cut from the story. If he'd stayed in, [[HeterosexualLifePartners Pullo and Vorenus]] would've gotten one hell of a reunion.
** A scene [[WhatCouldHaveBeen was present]] [[http://www.imsdb.com/scripts/Thor.html#6360 in the original script]] where Loki did reveal himself to Laufey [[spoiler: as his son]]. Laufey then admitted [[spoiler: his ParentalAbandonment of him]]. Therefore, Loki's [[AntagonisticOffspring antagonistic behaviour]] toward Laufey would have a more logical explanation.
** Dr. Selvig offered Jane to contact his colleague for consultation about SHIELD when SHIELD confiscated Jane's equipment. Said colleague was actually [[Film/AntMan Dr. Hank Pym]] and his name was initially going to be mentioned. But the filmmakers think it was too soon to mention Hank Pym, so his name ends up being unmentioned in the film.
** In the comics, Sif and Heimdall are siblings, which is not retained in this film and thus the rest of the MCU. At one point, this element was going to be retained and Sif would have been dark-skinned as well: [[http://www.comicbookmovie.com/fansites/MarvelFreshman/news/?a=40977 concept art of this exists (which also reveals that Baldur was originally going to be in the film before being cut)]]. This might be for the best however, despite that lost connection - besides Jaimie Alexander giving a strong performance, it would have probably [[UnfortunateImplications been uncomfortable for a number of viewers]] to see Thor rejecting his black Asgardian childhood friend in favour of a white ''human'' female.