Abandoned Warehouse: A derelict depot in London turns out to contain portals that lead to different worlds as part of the convergence.
Action Girl: Lady Sif's first scene is kicking marauder ass. Her second scene is practicing in Asgard.
Action Mom: Frigga gets in on the action, too, and easily defeats Malekith in a one-on-one fight.
Actually Pretty Funny: When Thor stops himself from punching his brother Loki, he says "[Mother] wouldn't want us to fight." Loki replies "Well she wouldn't exactly be shocked..." Thor can't help but laugh at that.
Among The Marauders, there is a Giant Mook called Berserker, a specific unit composed of unknown members of a large, rock-like alien species. It looks suspiciously like Korg, a heroic gladiator in the comics and an ally of The Hulk.
In the comics, Algrim/Kurse does work for Malekith for a time, but Malekith betrays him and Algrim—a noble soul—swears loyalty to Thor and Asgard, in fact being the one to kill Malekith himself. In this movie, Malekith does sacrifice his own people but doesn't betray Algrim personally. Algrim has Undying Loyalty towards his master and becomes Kurse as a result.
Adorkable: Jane while she's lying on the examination table in Asgard. She's so delighted by the new tech and asking so many questions that a visibly annoyed Eir has to tell her to be quiet and lie still.
Aerial Canyon Chase: The secret door to other dimensions Loki knows of is hidden in a tiny mountain crevice. He has to pilot the ship through it.
Alien Invasion: Played with. Although the Dark Elves do attack Greenwich, they're not there to conquer Earth, as the Chitauri were in New York. It just so happens that the perfect spot to amplify the Aether with the energy of the Nine Realms is located near Greenwich.note This actually makes sense, as in Norse Mythology, Earth is literally the center of Yggdrasil ("the World Tree"). If you're trying to spread darkness across the cosmos, why not start at literally the heart of the universe?
Aliens Are Bastards: The Dark Elves surely are this for wanting to exterminate all life in the multiverse.
Almost Kiss: Thanks to Darcy, but Thor and Jane get their kiss in later on Asgard.
The Anticipator: This trope is played with straight (Loki) and as an inversion (Thor). Some moments after Frigga's death, Thor visits Loki's cell and the latter acts as cocky as always as he has been expecting Thor. Thor, knowing that their mother is Loki's most important person, doesn't buy his bluff and tells Loki to drop the illusion. Loki then promptly drops it and reveals a messed-up room and his disheveled state.
Anti-Hero: Loki is an example of Nominal Hero; he's a convicted war criminal who's only going along with The Plan to save the world as a result of Frigga's death.
Annoying Younger Sibling: Loki knows how to get under Thor's skin, irritating the heck out of his brother with his shapeshifting pranks and his snarky comments about Thor's piloting skills during their escape from Asgard.
Apologetic Attacker: When Fandral takes out the Asgardian guards chasing after Thor and Jane, he quips "Nothing personal, boys!"
When Thor is at Charing Cross Underground station in Central London and asks how to get to Greenwich, the answer he is given — "Three stops on this train" — is impossible. You can get a mainline train to Greenwich from Charing Cross above ground via Waterloo East and London Bridge, but you certainly can't get there in three stops on an Underground train.
The Jubilee line goes across the Thames to Grennwich the stop is called "North Greenwich"
When Selvig is being apprehended by police at Stonehenge, a lot of tourists could also be seen in the background standing right next to the stones. With certain exceptions (summer and winter solstices, spring and autumn equinoxes, special bookings throughout the year), tourists are generally not allowed to even walk near the stones, much less get so close that they could touch them.
Attack of the 50-Foot Whatever: When Malekith unleashes the Aether during the apex of the Convergence, he becomes about five times taller than Thor. He returns to his normal height when Thor hits him incredibly hard with a an explosive impact.
Loki: Don't hit the buttons, press them gently. Thor:[hitting the buttons harder] I am pressing them gently! [...] Loki: Look, why don't you let me take over, I'm clearly the best pilot. Thor: Is that so? Of the two of us, which one can actually fly? [...] Loki: Now they're following us. [shots] Now they're firing at us! Thor: Yes, thank you for the commentary, Loki! It's not at all distracting! [fighter crashes a statue, destroying it] Loki: Well done! You just decapitated your grandfather.
The Bad Guy Wins: Playing with a Trope. The Dark Elves, the main villains, are defeated but Loki exploits the situation to usurp the throne of Asgard. Then again, whether he's a "bad guy" or not is a complicated question and Thor doesn't want the throne anyway.
Barrier Warrior: When Jane becomes possessed by the Aether, anybody attempting to aggressively manhandle her gets very violently deflected away.
Loki and Thor in Svartalfheim. Loki's Reliable Traitor status makes it very convincing for everyone — audience included — when he stabs Thor immediately after having his cuffs removed. Then he chases a tumbling Thor down a hillside, with Jane following, and cuts his hand off halfway through recalling Mjölnir as he calls out Thor on his sentimentality. As Malekith approaches, he grabs Jane and tosses her at them, asking for them to let him watch them destroy Asgard. The moment the Aether is out of Jane, Loki removes the illusion, and Thor blasts the Aether with enough lightning to put a Leviathan down. It doesn't quite work, but the effect was there.
The entire act of bringing Jane to Malekith so he can extract the Aether and Thor can attempt to destroy it is seen as this by Odin, which is why he wants to stare down Malekith in a frontal assault when Malekith comes to claim it in Asgard. Ultimately, while Odin's own plan is patently pyrrhic, he's proven right when Thor does indeed allow Malekith to leave with the Aether once Thor goes against his father's wishes and fails to destroy the Aether when it's pulled from Jane.
Big "NO!": Thor screams "NOOOOO!" when Frigga is slain and another one when Loki seemingly gets killed.
The end credits sequence includes individual credits with headshots of most of the cast, including Alice Krige (who only shows up in one scene) and Chris O'Dowd (who appears in two) — but not Jonathan Howard, who played the much bigger and more plot-significant role of Ian.
Bittersweet Ending: Thor is able to defeat Malekith and prevent the universe from being destroyed and ends up staying with Jane on Earth. However, he's lost Frigga and his brother, and unbeknownst to him, Loki faked his death and he has usurped the throne from Odin, whose fate isn't revealed.
Black Eyes of Evil: Jane has these several times as a result of being the host of the Aether. When on the Dark World she gains these as well as startlingly blue pupils, not unlike the Dark Elves'. When Malekith absorbs the Aether himself, he temporarily gets black eyes before reverting to red eyes with black pupils.
Blatant Lies: When Frigga asks, "Am I not your mother?", Loki hesitates for a full five seconds before he unconvincingly replies, "You're not." The sad expression on his face and his reaching out for her hand afterwards prove that he doesn't mean it.
Toned down considerably from the first film, as the stakes are much higher this time around. When Asgardians stop taking joy in battle and are just straight-up battling, you know it's deadly serious.
Volstagg, on the other hand, still loves to fight. When fighting against his fellow Asgardians, he's very visibly happy.
Boomerang Comeback: Mjölnir received the order to return to Thor's hand in the climactic battle, and come Hel or high water, it's gonna, despite his dimension-hopping! It was even flying up and away from Earth at one point because he ended up on another planet. Eventually, it does right in time to strike the final blow against Malekith.
A literal one. When the gang first discover the portals in London, one of them tosses in a brick, and it doesn't come back. Later, when Jane wakes up from being knocked out, the brick is seen in the background appearing out of nowhere and landing.
Later, we find the missing shoes and car keys as well.
At one point a pair of RAF jets fly into Vanaheim... and at the end of the big battle sequence, they fly out again.
Also, the second stinger shows the Jötunheim beast still running around Greenwich, chasing birds.
Britain Is Only London: Averted. While nearly all of the Earth scenes do take place in Great Britain, it's mentioned that Dr. Selvig had been going around other places in England such as Stonehenge.
The Brute: Kurse is this to Malekith and the entire Dark Elf race because he is the last of the "Kursed" and using Psycho Serum. This means he is tremendously powerful but dim witted and requires Malekith to direct him.
Upon his return to Earth, Thor tells Jane "I gave you my word I would return", as he promised near the end of Thor.
Loki has been imprisoned as punishment for his actions in The Avengers.
"That was for New York!"
Dr. Selvig's mental state is still a little fragile due to Loki's manipulations, also in The Avengers. He's also relieved when Thor tells him that Loki is dead.
There is a very brief scene in Jötunheim in which we see one of the giant creatures from the previous movie.
Loki refers to Thor's "new companions" and taunts him by shapeshifting into Captain America.
Odin reminds Loki that if he had not taken him from Jötunheim, he would not be alive today.
A sequence in the Battle of Vanaheim of Mjölnir hitting a Marauder and flying back into Thor's hand mirrors a similar sequence in the Battle on Jötunheim in the first movie.
Jane still has issues with SHIELD.
Darcy still calls Mjölnir "Mew-mew".
Volstagg empties his beer and throws the mug on the ground while shouting "Another!", which Thor did in the first movie. Luckily, Volstagg is in Asgard when this happens, so he doesn't get the stares Thor got.
One awesome call back that takes place during the movie; when Thor faces down the rock monster, he tells it, "I accept your surrender." before smashing it into pieces. He later tells Malekith the same thing before defeating him.
Heimdall is the only one aware that Loki has knowledge of secret doorways out of Asgard. In Thor, Loki revealed this to Heimdall just before freezing him with the Casket of Ancient Winters.
When Thor is holding council with Heimdall, Sif, and the Warriors Three (well, two of them), Sif mentions that the Tesseract is under heavy security - at the same time confirming it can still be used for travel between worlds a la Bifröst.
Loki stabbing Thor on Svartalfheim mirrors a similar scene in The Avengers.
Loki introduces himself to Malekith as "Loki of Jötunheim". This is a call back to both Thor, where his Jötunn origin was revealed, and The Avengers, where he introduced himself as "Loki of Asgard".
One of Loki's last lines in Thor is to Odin, after his failed attempt to destroy Jötunheim: "I did it for you, father!" Fast forward two movies, when Loki is "dying" after saving Thor from Kurse, Thor says that he will tell Odin of what he did, to which Loki replies "I didn't do it for him," showing how much Loki has changed since the first film.
When Thor offers to return his hammer to Odin, Odin refuses it because "Odin" is really Loki, and Loki knows from the previous film that he wouldn't be able to lift the hammer.
The Cameo: As Loki considers some disguises, he tries out Captain America - and proceeds to mock him mercilessly. Tom Hiddleston wore a Cap suit and did an impression of him while staying in character as Loki, and Chris Evans' performance was based on that.
Captain Obvious: Loki, telling Thor that the other ships are firing at them.
Loki: Now they're following us. [shots] Now they're firing at us! Thor: Yes, thank you for the commentary, Loki! It's not at all distracting!
Car Fu: In the climax, Ian uses a car that has been rendered weightless (but not massless) by the convergence to crush a pack of Dark Elves.
Casual Danger Dialog: Happens at least once between Thor and Sif, with her commenting that everything was under control and him asking with a grin if that was the reason everything was on fire. Plus:
[a Kronan enters the fray as the Marauders cheer on] Sif: All yours.
The Chains of Commanding/Reluctant Ruler: Discussed during the denouement of the film between Thor and Odin: with Thor witnessing how the challenges Odin were facing for the rest of the film have taken their toll on him (see Not So Different below), Thor seems to have decided to not succeed as Asgard's king, but promises to be an independent protector of the Nine Realms. Which Odin seems to have peacefully accepted, if only because he's actually Loki in disguise, having usurped the throne.
Chekhov's Gag: Ian losing the car keys by tossing them in the portal and finding that not everything thrown there comes back is funny - and comes back later when Jane finds the keys in the dark world, showing her where the portal is. Turns into a Chekhov's Gun when she uses them to drive the car they had left behind in order to get to Greenwich.
Chekhov's Gun: Jane's distinctive cell phone ringtone is crucial for Jane and Thor to escape the Dark Elf homeworld through a portal that the reception is going through.
Frigga is a master of illusion, who taught Loki most of what he knows in that regard. She uses these abilities to first visit Loki in his cell, then later to hide Jane.
Loki's shapeshifting, which is Played for Laughs during the escape from Asgard. He uses the ability to create illusions and project illusions over others to persuade Malekith to draw the Aether out of Jane. Later, he uses these abilities to infiltrate Asgard and usurp the throne in the guise of Odin, even using the same guard disguise.
Clingy MacGuffin: Jane unwittingly becomes the host to the Aether, a shapeless mass of energy, and part of the movie is trying to remove it from her while it serves as the MacGuffin for Malekith, who wants to use it for his own reasons.
Coincidental Broadcast: While Darcy tries to get into contact with Erik Selvig, a news report comes on the television revealing where he is: locked up in a mental ward for running around Stonehenge completely naked. It's justified by the fact that it's a repeat of the news story reported earlier when Jane provides exposition about his mental breakdown and mentions not being able to contact him earlier.
Colony Drop: As a last ditch attempt to defeat Bor's forces, Malekith disables all of the Dark Elf ships hovering above Svartalfheim and tries to drop them on the soldiers.
Cool Versus Awesome: The movie can best be summed up as alien elves in starships vs. space vikings in flying longboats with lasers.
Costume Porn: Like in the first film, the Asgardians' clothes are beautifully detailed.
Could Say It But: At the end, Thor refuses the throne, believing himself a better guardian if given the freedom to come and go as he pleases. Odin insists that he cannot personally condone Thor's actions, nor can he tell his son how proud he is of him for doing so. Except it's not really Odin...
The Cuckoolander Was Right: Dr. Selvig is placed in a mental ward, but his theories about the Convergence are true. He also had legitimate mental problems that justified putting him in a hospital. However, when he realizes he was right all along, he tosses the enormous bag of meds he's been prescribed.
Selvig: There's nothing more reassuring than realising that the world is crazier than you are.
For the bad guys, the Dark Elves overrun Asgard's defenses thanks to Kurse sabotaging them, and the only reason they retreat is because Malekith was injured by Thor.
Kurse starts off giving one of these to Thor, pummelling his face into the ground and throwing boulders at him.
Curse Cut Short: Darcy gets a "sh-", when Malekith's spaceship decloaks and buries itself in the quad of the Royal Naval College.
D - K
Darker and Edgier: The color scheme alone is a lot grimmer, there's a full-scale war, and Thor claims this time he's ready to kill Loki if his genocidal sibling steps out of line. Hell, even the title reflects this. On the other hand, there's still a lot of humor, and much of the final battle is a mix of humor and action.
Dark Is Evil: The "Dark Elves" are the antagonists of this film because they want to snuff out the light of the universe and return it to darkness.
Deadly Upgrade: The Kurse power up works like this. The transformation looks painful but whether 'consumed' means the body will burn out in due time or until the warrior falls in battle is not made clear.
Deflector Shields: Asgard's main citadel is defended with one. This is why Algrim takes out the main engine and disable it.
Demoted to Extra: Hogun the Grim's role is reduced to two brief scenes from the already sparse screentime he had in the prior film, having decided to stay in Vanaheim. In contrast, the rest of the Asgardians receive expanded roles.
Derelict Graveyard: Svartalfheim is full of wrecked spaceships, a relic of the Dark Elf - Asgard war millennia ago.
Destructive Savior: Sure, Thor intends to save Asgard from Malekith's impending invasion - but he's caused a lot of property damage in the realm during his dashing, "treasonous" escape from Odin's pursuit, including (but not limited to) the humongous monument of his grandfather Bor, King of Asgard before Odin himself.
Disturbed Doves: Starlings are disturbed and flying in an erratic manner just before the elves invade Earth.
Double Meaning: When an Einherjar "soldier" comes to report Loki's death to Odin, the Allfather looks distressed and says, "Loki!" The in-universe explanation is Odin is upset over the loss of his son, but it's also a hint to the audience, since the soldier is Loki!
The Dragon: Algrim/Kurse is this to Malekith; chief enforcer and most powerful minion.
Loki: I thought you said you knew how to fly it. Thor: I said, "How hard could it be?" [several crashes later...] Loki: I think you missed a column. Thor: Shut up.
Dungeon Bypass: Instead of a long, prolonged battle with Malekith's army to get the Aether, Bor elects to just teleport the Aether back to Asgard with the Bifröst before the war even ends.
Early-Bird Cameo: The Collector, from the upcoming Guardians of the Galaxy film, shows up in the mid-credits Stinger.
Eldritch Starship: The Dark Elf capital spaceships resemble floating towers or skyscrapers, menacingly glow with red lights, and generally look otherworldly and unsettling. The smaller fighter/transport ships appear to mostly consist of a massive blade/battering ram, and have no symmetry axes whatsoever, making it nearly impossible to tell which side up are they supposed to fly, anyway.
Elves VS Dwarves: Played with. While they don't exactly match the respective archetypes, armies of Svartalfheim and Asgard fit the general aesthetics of the conflict (somewhat ironically there was little difference between the Svartalfar and Dwarfs in Norse Mythology). Also inverted in some cases. Technology styles: the "Dwarfish" Asgardians use magicked-up medieval weapons (spears, hammers, skiffs), while the Dark Elves use high tech spacey weapons (beam weapons, grenades, starships).
Even Bad Men Love Their Mamas: The one time Loki shows any true, sincere emotion in the film was in the solitude of his cell, without any witnesses as he smashes the furniture around him in grief at the news of Frigga's death. Later, when Thor asks him to dispel the illusion, he hasn't bothered to clean it up at all, and appears notably unkempt. In his first scene, Loki puts on a contemptuous façade, but his mask slips when Odin informs him that he will never see Frigga again; he then stumbles as he's being led away by the guards.
Evil Is Petty: During the attack on Asgard, Malekith takes the time to destroy Odin's throne.
Evil Overlooker: Malekith in one of the posters and when he witnesses his fellow Dark Elves awakening.
The camera lingers on Thor's naked torso as he bathes. Why is the scene in the movie? According to Chris Hemsworth, Joss Whedon wrote this scene in as one of comfort after a battle.
Minor case in the post-credits stinger. When Jane and Thor embrace and kiss, her back is to the camera, and she's wearing noticeably tight pants. Elsa Pataky (real life wife of Chris Helmsworth) stood in for Natalie Portman during that scene.
Final Solution: Bor's answer to the constant threat of the Dark Elves, which Odin grinned about when recounting. Justified in the Dark Elves were constantly trying to destroy all life in the multiverse. Ironically, Malekeith contributed his own fair share to this to cover his escape.
Fish out of Water: Last time, Thor struggled to adjust to the world of Earth with Jane as his guide. Now the roles are reversed and it's Jane's turn to adjust to the other worlds of the Nine Realms. Surprisingly, she's quite comfortable with it.
Force-Field Door: Asgardian prisons utilize this technology. A similar technology is used as Deflector Shields which cover the main Asgardian citadel. Predictably, they both fall to Kurse.
Foreshadowing: Loki briefly impersonates an Einherjar warrior during his and Thor's escape from prison. Loki later impersonates such a warrior, possibly the same one, after his apparent "death" in order to sneak back into Asgard. There's also a telltale green glow during the second instance.
In the same instance, the transformation of Thor into Sif shows that he's able to project illusions/shapes onto other people, thus making the Batman Gambit possible.
Full-Name Basis: Asgardians almost exclusively address Thor's girlfriend as "Jane Foster", seemingly unfamiliar with Midgardian given names and surnames.
Gainaxing: Jane gets some prominent slow-motion jiggle in the library near the climax.
Gender Bender: Temporarily done to Thor by Loki as they are escaping from Asgard, transforming him into Sif as a joke.
Generic Doomsday Villain: Malekith the Accursed is out to destroy the universe and return everything to darkness. Why? Because light annoys him and he wishes it was gone. He's less a character and more a plot device to justify having Thor and Loki team up. Apparently they had intended to flesh out Malekith's character through additional scenes (according to Christopher Eccleston, his actor) but it was excised from the film proper (might show up as deleted footage or some other supplementary material in the home release).
Becomes a Running Gag when all of Thor's friends in Asgard tell Loki the same.
Loki: Evidently, there will be a line.
Genre Shift: With the introduction of Dark Elves, and increased screen time for Asgard, the film drifts towards Science Fantasy in terms of look and feel. At times it verges on Space Opera, with battles between ships and gun batteries full of laser fire and holographic interfaces, and much more travel to other worlds.
Loki: If I'm in for the axe, then for mercy's sake, just swing it.
Gilded Cage: Thanks to Frigga intervening on his behalf, Loki's prison cell has fairly lavish furniture and looks very comfortable — but it's just as confined as the others.
A God I Am Not: When Loki tries to claim that he merely intended to rule Earth as a benevolent god, Odin counters that they're no more gods than Earthlings are. Loki counter-counters that they live a whole lot longer.
Gravity Screw: The effect of the nine realms aligning themselves. Some things float, some bounce between different points or pop up in unexpected places. This is explained as the borders of the realms blurring.
Heel-Face Revolving Door: Unsurprisingly, Loki. He switches between a staged betrayal of Thor in front of Malekith to him protecting Jane and seemingly sacrificing himself for Thor to usurping the throne from Odin behind Thor's back.
Helmets Are Hardly Heroic: Once again, Thor, Sif, nor any of the Warriors Three wear a helmet, and Loki notably never wears his enormous horned helmet from the previous movies where he was the main villain.
Loki pushes Jane out of a grenade's path and nearly dies before Thor saves him. Later, he takes out Kurse at what seems to be the cost of his own life... and then subverted when it turns out he's Faking the Dead.
Frigga refuses to reveal Jane Foster's location, even when threatened with certain death. She's murdered for her efforts.
Hypocritical Humor: In a scene from the trailer, Loki tells Thor he can't solve all his problems by hitting things. This from a guy who's twice tried to fix his self-image problems by destroying planets.
I Choose to Stay: Thor abdicates from his duties to the throne of Asgard to protect the Nine Realms and live on Earth with Jane.
I Have No Son: Odin makes it pretty clear that he no longer considers Loki his son and would've have had him executed if weren't for Frigga.
I'm Not Hungry: Jane Foster says this word for word while rejecting a meal brought by a guard. It turns out it wasn't a guard at all but Lady Sif in disguise, pretending to bring Jane food in order to rescue her.
"I Know What We Can Do" Cut: When Thor decides to go after Malekith, which requires overcoming numerous obstacles starting with the fact that Odin has forbidden him to leave Asgard, the ensuing sequence alternates between Thor explaining his plan to his friends and the plan being carried out.
After Frigga dies, Odin wants to face the Dark Elves on a martial basis, while Thor is proposing a more peaceful solution. This is the exact reverse of their positions at the start of the first film.
In the film's prologue, Malekith crashes all of his ships into the surface of the Dark World to destroy as much as of the Asgard army as possible, killing most of his race in the process. In the climax, Malekith is killed by being crushed beneath his own ship on The Dark World, surrounded by the wreckage of his previous war crime.
Invisibility Cloak: The Dark Elves vessels, which Heimdall only notices when they're virtually on top of him. He takes a major hit in his confidence over this.
It's Personal: Malekith killing Frigga is this for the Asgardian royal family. Even Loki, for all his posturing, is wounded by the news and agrees to assist Thor's campaign of treason in order to get at Malekith. He even tells Thor to "trust his rage" even if Thor cannot trust the man himself, certifying how his desire for vengeance overrides any other element of his personality.
Jacob and Esau: It seems that Loki was his mother's favourite, while Thor was his father's; each of them gave their favorite their icon tools, illusions and a hammer respectively.
The Juggernaut: Kurse breaks out of prison by smashing shields, tears through the city guards, rips open locked doors, kills a Lady of War and demonstrates to be unstoppable. He could only be taken down with his own black hole grenade.
Just Desserts: A Dark Elf is eaten by a Jötunheim beast accidentally teleported to Earth.
Just Hit Him: Averted. Kurse is much stronger than Thor, willing to literally beat him into the ground.
Karmic Death: Malekith orders a Colony Drop that kills millions of his own people while trying to escape the Asgardians. He later dies by having a ship dropped on him.
L - P
Lady of War: Both Sif and Frigga are graceful and lethal fighters.
Last Of Their Kind: Malekith and his ship's inhabitants are all that remain of the Dark Elves. By the end, it's safe to say that they've been wiped out altogether. Algrim is the final Kursed, be it a lost art/technology or it has some further significance to Malekith.
Legacy Character: The Kurse powerset and name is given to dark elves if they've proven worthy in the eyes of Malekith. Algrim is such an elf.
Leitmotif: Hilariously, Steve's turns up when Loki turns into Captain America and proceeds to mock him mercilessly. This makes it the first theme to appear in three MCU movie series, as it also makes a cameo in The Avengers.
The Living Dead: As Thor cradles Frigga's body after she was slain by Algrim, you can see her breathing (accentuated by her belt pouches moving up and down).
Lodged Blade Recycling: During the fight on the Dark World, Loki stabs Kurse through the back with a sword that comes out his chest. Kurse turns around and impales him on the blade that is sticking out of his chest.
Logo Joke: In the trailer, the red background in the Marvel logo moves to show Thor's cape.
Long Lived: It turns out that Asgardians aren't immortal gods, according to Odin. They're born, live for at least five thousand years according to Loki, and eventually die. This has some basis in Norse Mythology, as the Aesir were established as capable of dying (in fact, Ragnarok has a pretty detailed list on how some of them will die). The only way the Aesir were able to retain youth was from eating Idunn's apples; since the MCU has Adapted Out these, it stands that the Asgardians would eventually succumb to old age. (Golden apples can briefly be seen in Asgard in the first film, but aren't identified as having any special properties.)
Loophole Abuse: Heimdall is bound to report any knowledge of treason to Odin. So he summons Odin and the guards to Bifröst to inform them that he's committing treason, which he is - by failing to report the treason also being carried out at that very minute all the way back at the palace.
Frigga, on the other hand, has never shown anything except respect, amicability and concern for Jane, even going to the extent of protecting her with her life from Malekith, although whether that's really for her or for the Aether possessing her is muddy.
Luxury Prison Suite: Loki's cell is lavishly furnished and quite comfortable, but as confined as the others. Justified, as his mother mentions bringing him books. It can be assumed she tried to make him comfortable, too.
Magic Versus Science: A downplayed version with both sides using Magitek. The Dark Elves focus more on beam weapons and artificial black hole grenades, using space ships to travel, but beef up their elite troops with magic. Asgardians focus on using close combat pre-industry weapons and travel by the Bifröst, but have beam batteries and Viking-vessels for defense.
Magitek: As always, the line between the Asgardian's magic and their technology is so blurry they don't bother to make the distinction. Jane is able to identify the medical device they put her in. They call it a soul forge, she calls it a quantum field generator.
Mayfly-December Romance: Odin and Loki both remark on this concerning Thor's relationship with Jane. A human's one hundred year life span is "a heart beat" compared to Aesir who can live for thousands of years.
Medieval Stasis: The Asgardians are an interesting case. They are a society caught in medieval stasis that is advanced far beyond medieval times. They are shown using the same weapons (swords, shields, and spears), technology, and armor 5,000+ years ago as they do in modern times. Horses are a common form of transportation. Yet they can harvest material from stars, have flying machines, and travel between worlds through wormholes. Implied to be a combination of their extremely long lives, emphasis on close combat, use of magic, and being at the top of the food chain so long and eliminated all of society's ills that they have no reason to change.
Mineral MacGuffin: Discussed. Odin notes that most objects of power are gems, but the Aether is a fluid.
Misfit Mobilization Moment: The final battle has all of the human characters, all of whom are varying degrees of quirky, band together with Thor and remind the viewers that they're also brilliant scientists (and that Thor is a tactician as well, if a boisterous one) - pushing back the invading forces and executing a plan that ultimately defeats Malekith with science when brute force failed.
Jane inadvertently ends up doing this to Darcy, warping her in just as she's kissing Ian.
Moment of Silence: Comes up after Frigga is killed by Kurse. Thor burns half of Malekith's face as this happens and tries to attack him more as he escapes.
Monumental Damage: The Old Royal Navy College takes the brunt of the Dark Elf attack. Other London landmarks (such as Saint Paul's cathedral and the Gherkin) sustain minor damage. The former was originally scripted to be devastated in the fighting, but this was changed at the explicit request of Saint Paul's. They wanted the cathedral depicted relatively unscathed in the aftermath when much around it was smoking ruins as a callback to it surviving The Blitz.
A somber Viking Funeral scene is followed by Dr. Selvig's insane lecture in a mental ward.
Malekith manages to bring Thor down with the Aether and tries to pummel him. Cue them teleporting above London's St. Mary Axe (Also known as the "Gherkin") , cracking it and sliding down the windows with onlookers watching them fall. In addition to this, following a few more random moments of warping that see Thor struggling to summon Mjölnir back to his hand, Thor ends up in a London Underground station. He quickly asks a bystander how to get back to Greenwich. She says by taking the train she's on for three stops, which Thor responds to by calmly boarding the train and commuting back to the battle.
Not long after Thor is mourning Loki's supposed sacrifice, Jane's phone rings with a rap ringtone.
After being reunited with Thor, Dr. Selvig asks (very nervously) about Loki's whereabouts. Thor somberly delivers the news of Loki's apparent death, to which Selvig cheerily replies, "Oh thank god!" To Selvig's credit, he quickly catches himself and offers his condolences after seeing Thor's reaction.
Mordor: Svartalfheim is a bleak, ash-covered wasteland.
Mr. Fanservice: Thor, naturally. There's even a hilarious blatant pair of shots devoted to his magnificent chest and equally glorious back, both glistening with water from a sponge bath.
Thor's latest costume is inspired by his 1980s comic book incarnation; the same era that introduced Malekith.
Thor hammers a Kronan (or a Stone Man From Saturn as they were dubbed back in the Silver Age, where they served as the first ever villains Thor fought).
Malekith seeks Jane for his own purposes. He used Sif in a similar manner in his first appearance.
Odin gives a nod to the actual Norse mythology when he states a goat doesn't belong at a banquet table.
Malekith getting half his face burnt makes him look more like the comic book Malekith, whose face was half white and half black.
During Selvig's rambling lecture about the Convergence, a circled "616 universe" can be seen in the center of the blackboard. This refers to Marvel's designation for the mainstream comic continuity.
Malekith and Kurse had first appeared in comics at The Surtur Saga. There's a point of that story adapted into the film as well: Loki seems to betray the Asgardians for Malekith, but he was actually a Reverse Mole all the time.
Odin suggests that Thor should forget Jane Foster and focus on what's "in front of him", while the two are looking at Sif training for battle. Besides the obvious point (Odin would prefer Thor to be with Sif instead of Jane), this could be a subtle nod to the comics, where Thor's romantic relationship with Jane ended a long time ago, and after that he's had an on-again, off-again relationship with Sif for years. (Note also that in the actual Norse myths, Sif is Thor's wife.)
When Thor offers to relinquish Mjölnir, Odin tells him that it is his "if you are worthy." In Thor's first Marvel appearance, the inscription on the hammer says the one who finds it "if he be worthy, shall possess the power of Thor." This led to reader questions on what happens if someone else who is worthy finds it, and eventually the Beta Ray Bill storyline.
Thor mentions Sif's boisterous behavior after "the Battle of Harokin". In the comic, Thor and his friends battled Harokin and Hela in issues 129-31
The second track of the soundtrack is entitled Lokasenna, the name of a poem in which Loki systematically insults the gods at a banquet until Thor shows up.
Naked People Are Funny: Erik Selvig runs around Stonehenge while doing his research in his birthday suit due to the insanity he gained from being mind controlled in The Avengers.
Never Bring a Knife to a Gun Fight: Asgard's troops are initially outmatched when the Dark Elves first breach Odin's palace when the shield is lowered, as the Dark Elves carry laser rifles and Asgard's soldiers are only armed with swords and shields, causing a fair number to get shot as the Elves pour out of their craft. However, once the Asgardian forces can get within melee range, the battle becomes more contentious.
Back in full force with Loki's character. From his conversation with the Frigga illusion she conjured to visit him to a conversation with Thor in Svartalfheim, he constantly says that he did nothing to deserve his punishment.
Loki: Who put me there? WHO PUT ME THERE?! Thor: [grabbing Loki by the throat and slamming him against the side of the boat] You know damn well! YOU KNOW DAMN WELL WHO!
Malekith blames Asgard for the Colony Drop he himself ordered that annihilated his own people.
The trailer has Loki commenting, "Hitting doesn't solve everything, brother," while Thor takes down a troll. In the theatrical cut, Loki's nowhere near Vanaheim during the time of the battle.
During the trailer, the dialog between Thor and Heimdall discussing Loki implies that Loki has had dealings with the Dark Elves. In the actual movie, nobody's interacted with the Dark Elves for thousands of years. What Loki knew was the secret portals that can be used to leave Asgard.
The trailer also removes all of Loki's broken furniture, hiding his breakdown after Frigga's death.
The trailers suggested that there would be a Love Triangle between Thor, Sif, and Jane. This plot amounts to a single conversation between Odin and Thor, and a slight bit of tension between Jane and Sif that doesn't have an influence on the story.
Malekith's invasion of Greenwich appears in the beginning of most trailers, implying this is the start of the story as well. In fact, it's the last act of the movie.
The scene where Thor recruits Loki was altered for the trailers: In the trailer Thor says, "You should know that when you betray me, I will kill you," while in the movie Thor makes a short speech saying that while he may have retained some hope of redeeming Loki in the past, he doesn't anymore, and that if Loki betrays him Thor won't hesitate to kill Loki.
In trailers, the scene where Thor and Loki are walking together down a hall was edited to look like a Power Walk, with fans thinking the scene would be a Moment Of Awesome the first time the trailer was shown. In the movie, it's a very humorous scene, with Loki teasing Thor the whole way.
For Odin: If Odin had listened to Thor when he argued that their best course of action was to take Jane off Asgard so Malekith wouldn't target them a second time in order to get the Aether, Thor wouldn't have sprung Loki from his cell and subsequently the actions that led to Loki usurping the throne of Asgard would not have come to pass.
More directly, there's Thor's plan: instead of staying at the heavily fortified Asgard, with literally an army at his beck and call, Thor heads to the Dark World with Loki and Jane, who's carrying the Aether, the superweapon needed for Malekith to destroy the universe, then tries to destroy it as Malekith draws it out of Jane. The result? Thor fails completely and all but literally hands over the Aether to Malekith on a silver platter. This at least manages to save Jane's life. Though from Thor's perspective, it costs Loki his. But the truth is even worse... it put Loki on the throne of Asgard.
And in the stinger, apparently the Asgardians aren't Genre Savvy enough to avoid giving one of a set of Infinity Stones to a guy called "The Collector".
Loki's not exactly a hero, but if he hadn't told Kurse which staircase to take out of the prison, the Dark Elf might not have been able to bring down Asgard's defensive shield to let Malekith in... and Frigga might not have died.
Nobody Poops: The prison cells on Asgard, holding prisoners from across the worlds and realms, are all constantly sparkling-clean and white-walled/floored with no evidence whatsoever of being equipped with toilets/latrines during the scenes where they appear.
No, Except Yes: In the first scene, before Loki is led to prison, he speaks with Odin.
Loki: It's not that I don't love our chats... It's just... I don't love them.
No Man of Woman Born: Kurse is told that no power the Dark Elves' enemies possess will be able to harm him. True enough, he's killed using his own weapon.
No Medication for Me: After being sprung from the Asylum, Selvig throws away his big bag of prescription medicine. In his case, it seems that the medication was either genuinely unneeded or reacted badly with him, because he spends the rest of the movie far more stable, if still a bit strange.
Nonchalant Dodge: During the Portal Cut moment with the police car, Heimdall leans to the side a bit so the bumper just sails past him harmlessly.
Noodle Incident: Thor at one point chides Sif that she had so much fun celebrating the battle of Haragon that she nearly started a second one.
Not Me This Time: Thor's first thought when he hears rioting in the prison is, "Loki." Actually, he's about the only prisoner not involved in the riot started by Algrim.
During Odin and Loki's first scene together, Loki points out that his actions in leading armies to subdue and conquer the other realms is Not So Different from Odin (and Bor's) own war-torn history. Odin doesn't really address this, except by denying that Loki was ever in line for the Asgardian throne and thus has no birthright.
A subtler example is how Thor and Loki have influenced each other's abilities and mannerisms. Thor has learned some trickery and sarcasm from his adopted brother, while Loki has become a braver and stronger melee fighter.
Odin chastises Loki for thinking he's superior to humanity, and insists that Asgardians are just as mortal (give or take 5,000 years). Later when Thor brings Jane to Asgard for help, Odin tells him off for it because sickness and death are defining characteristics of "mortals," and that Thor should have left her. Further reinforced by first Odin and then Loki advising Thor that a Mayfly-December Romance between him and Jane Foster will never work out.
Out-of-Character Alert: When it looks like Loki's betraying Thor, he introduces himself to Malekith as "Loki of Jötunheim". Anyone who recalls the first film will know that Loki hates his true parentage, therefore cluing us in that something is amiss. There was; the betrayal was a ruse to get the Aether out of Jane so that it could be destroyed. Even before that, there's his line: 'Did you really think I cared about Frigga?'. And he does.
OOC Is Serious Business: Loki destroying his cell's furniture in solitude when after being informed that his mother is dead. This is an indicator to the audience that despite Loki's Chronic Backstabbing Disorder and otherwise collected and manipulative personality, his desire to see Malekith pay for what he's done and alignment with Thor if he must is unshakable ("trust my rage"), even if it would appear otherwise...
Early on when Darcy interrupts Jane's dinner to present her findings (ie. first signs of the convergence):
Jane: "It's malfunctioning." Darcy: "That's what I said. (Jane starts knocking the device) That's what I did!"
Becomes a Not So Different moment later when Thor starts pounding the spaceship controls.
Personal Raincloud: Inverted. The first clue that Jane now has something nasty looking out for her is that she and Darcy are in a rainstorm, brought about by the approach of Thor, but inexplicably in the middle of a dry circle; Jane's being protected from harm, which apparently includes rain. Then Jane sees Thor and runs over to him and the circle follows her, leaving Darcy soaked.
Pet the Dog: During the battle against Malekith and the Dark Elves, Kurse throws a black hole grenade at Loki and Jane. Loki pushes Jane aside without thinking and almost dies as a result. You'd think Loki only did so to gain Thor's trust, thus setting his own plan in motion (faking his death, usurping the throne of Asgard disguised as Odin and ensuring that Thor would want to stay on Earth with his human girlfriend) but it was too spur of the moment to be planned, even for Loki.
Pietà Plagiarism: Loki is the recipient of this when Thor cradles him in his arms after he's stabbed by Kurse.
Pineapple Surprise: Loki pulls this trick on Kurse; detonating the grenade he is carrying on his belt.
Portal Cut: When Thor takes Jane to Asgard, the Bifröst clips the front end of a nearby police car. The bumper tumbles out the other end a few seconds before Thor and Jane arrive. Later on, Malekith loses a couple of limbs to Selvig's gravitational spikes, which have been reconfigured to open rifts.
Precision F-Strike: An extremely unusual example: in a scene where Malekith is speaking Elvish it distinctly sounds like he says- in English- "I fucked up." The line was edited in the home video releases.
Prison Riot: Algrim, posing as one of the captured marauders, starts one in the dungeons of Asgard as a part of Dark Elves' plan to attack the place and collect the Aether from Jane.
Put on a Bus: Hogun leaves Asgard for Vanaheim early in the film, so he is absent for the rest of the film save a fleeting reaction shot at the climax.
Pyrrhic Victory: Odin, stricken with grief over his wife's murder, is willing to "win" such a victory by allowing the Dark Elves to invade Asgard a second time. Thor tries to point out that this is crazy and a reckless waste of his people's lives, but Odin's fury blinds him to it.
R - Z
Racial Remnant: Malekith's crew of Dark Elves are all that remain of them.
Ramming Always Works: This appears to be the principle behind the smaller Dark Elf "Harrow" craft: they have no ranged weaponry apart from guns protecting the entrance, but are very resilient and shaped like flying daggers that ram and destroy Asgard's fighter skiffs or fortifications.
Reality Is Out to Lunch: During and shortly before the Convergence, reality, especially around Greenwich on Midgard, is extremely volatile. Portals open and close at random to different worlds, and Gravity Screw is all over the place. This issue solves itself after the Convergence ends.
Dr. Erik Selvig: There is nothing more reassuring than realizing that the world is crazier than you are.
Recruiting the Criminal: Thor enlists Loki's help due to his ability to find ways out of Asgard no one else is aware of.
Red Right Hand: Malekith is disfigured on one side of his face thanks to a blast of lightning from Mjölnir.
Red Shirt Army: The Einherjar are dedicated enough but still mostly helpless against the more technologically advanced Dark Elves. Averted in the prologue, where the Einherjar under Odin's father Bor eventually overcome the Dark Elves. It probably helps that they were mobilized for an invasion, as opposed to being caught flat-footed on their own soil.
Revenge: After Frigga is murdered, this becomes Loki's motivation to team up with Thor to stop Malekith.
Revenge Before Reason: Odin slips into this after Frigga's death, with Thor pointing out that he's no better than Malekith if he's willing to throw away the lives of his own people in the name of victory.
Ridiculously Difficult Route: Loki and Thor use a secret "back door" from Asgard. This involves flying a ship at top speed into a tiny crevice in a very rocky mountain, with, one can imagine, disastrous consequenses if one misses. Even with Loki's 'expertise' they barely avoid crashing on their way out.
Loki: If it were easy, everyone would do it.
Roaring Rampage of Revenge: Loki's motivation for working with Thor and tracking down Malekith. Thor does it for the sake of averting a bloody conflict with the Dark Elves but Loki doing so is purely to see Malekith suffer.
It doesn't matter much since this is a comic book adaption, but in Norse Mythology, "Svartálfar" (Dark Elves) are sometimes interpreted to actually be the dwarves.
The Einherjar, in both the Norse myths and the Marvel comics, are the souls of the glorious dead feasting in Valhalla. In here, they are Asgard's city guards. They pull guard duty in the comics, too, as well as forming the bulk of Asgard's armies. Also, one could argue that guard duty is just their day job in-between feasts in the hall of Valhalla.
Schizo Tech: Early in the movie, just after the opening, Thor and his pals are seen battling some foes. At least one of them has a rifle... that shoots arrows.
See You in Hell: Loki says this to Kurse right before killing him, while seemingly mortally wounded himself. A Mythology Gag in that not only is Hel (sic) a location from Norse Mythology (and the comics, for that matter), but it's also the name of a person who, in the original myths, was Loki's daughter.
Sequel Escalation: In Thor and The Avengers, only one of the Nine Realms came under threat. In this film, Malekith threatens to erase light from the all the universe.
Sequel Goes Foreign: The first film took place in New Mexico. This one, all scenes in Earth are in London.
The scene at the beginning with an abandoned building with strange physics is highly reminiscent of the "Beyond" segment of The Animatrix, especially the gravitational anomalies and oddly behaving bottles.
The Dark Elf fighters resemble the B-wings, also from Star Wars.
Bor's helm looks a lot like a Balrog's head and horns.
Thor and Malekith sliding down London's Gherkin may be a Shout-Out to the climax of Adventures in Babysitting, where a Thor-obsessed/costumed little girl gets stuck on the windows of a similarly transparent skyscraper in Chicago.
When Fandral covers Thor and Loki's escape, he swings from ship to ship on a rope, much like Errol Flynn, who the character is based on, is famous for doing.
Sibling Team: Thor and Loki join forces to fight the Dark Elves.
Slap SlapAlmost Kiss: When Thor makes his first appearance after leaving her two years ago, Jane slaps him, then apologises, explaining she's just checking that he's real given the Reality Is Out to Lunch events she's just witnessed. She then slaps him for not coming back to her, despite turning up in New York. When Thor comes up with a reasonable excuse, they lean in for the inevitable kiss...then Darcy provides a Moment Killer.
Something We Forgot: The final stinger reminds the audience that the giant beast from Jötunheim is still loose on Earth.
Space Pirates: The Marauders, whose ranks are comprised of various criminals originating from different worlds; some of which aren't counted among the Nine Realms.
Space Romans: The Asgardians are mostly based on the Vikings while the people of Vanaheim, Hogun's homeworld, are based on Asian cultures such as Mongolia and Tibet.
Speak Ill of the Dead: When Selvig learns about Loki's apparent death, he's filled with glee and joy. He changes his expression accordingly once he sees Thor's reaction.
A mid-credits scene has Sif and Volstagg giving the remains of the Aether to the Collector for safekeeping in his vaults. The two Asgardians mention both the Aether and the Tesseract being Infinity Stones, and not wanting them near each other. The Collector takes the Aether and, after the two depart, smirks and says, "One down, five to go."
The post-credits scene has Thor reunite with Jane back on Earth, then shows the Jötunheim beast in London chasing some pigeons.
Standard Female Grab Area: Notably averted. When Loki grabs Jane, he picks her completely up off the ground by the waist. This is due to anyone grabbing her by the arm being blown back by the Aether that resides within her.
Staring Down Cthulhu: Loki does this to Kurse during the Prison Riot when Kurse walks by his cell, wondering if he'll break him out. Kurse seems to consider, but to him, Loki apparently didn't look useful. According to behind the scenes commentary, Kurse actually decides against letting Loki out of his cell because he realizes that a guy locked up by himself in an Asgardian prison and does nothing but smirk menacingly at people who walk by is probably too dangerous to let out. Kurse basically leaves Loki where he is because he can tell that he is bad news, not because he did not look useful.
Super Cell Reception: Jane gets a signal in the cave on Svartalfheim where all the stuff that teleported in the beginning of the movie ended up. It helps her find a rift back to Earth after she and Thor have been stranded there.
"Costume is a bit much. So tight! But the confidence...I can feel the righteousness surging!"
Teleport Spam: An uncontrolled version: in the final battle, the convergence has turned reality into swiss cheese, so Thor and Malekith (and various other things) end up teleporting between the realms constantly during their slugfest. For added trouble, Thor's attempts to recall his hammer keep failing because they keep ending up in different realms.
While they don't go full Xena, Jane and Darcy are much more proactive in this movie and make a major contribution in the final battle.
Loki is a much more effective melee fighter in this movie than in his previous appearances; here he was armed with only a simple dagger and took on several foes at the same time. In the past, he relied on throwing magical "knives" from a distance, his illusion spell, or a powerful scepter, and he usually focused on one enemy at a time.
Averted when the college students at Greenwich don't run away as advised.
"You're joking, right? That's Thor out there, waving his hammer about and everything!"
Downplayed when Thor gets into a London subway car in his full warrior regalia and asks for directions to Greenwich. There are some stares, one woman captures Thor on her mobile phone, and fake stumbles into him as the train pulls away in a blatant ploy to make some physical contact. Unlike the students, they don't want to make a scene.
Vanity Plate: A new one for Marvel Studios along with a fanfare (by this film's composer Brian Tyler) debuts in this film.
Loki shows uncharacteristic bravery and willingness to put his life on the line for others during his team-up with Thor.
Algrim is unquestioningly loyal to his master and offers to sacrifice himself if it helps to advance his Evil Plan.
Voluntary Shapeshifting: One of Loki's powers is the illusion variety. When Thor busts him out of his cell, Loki suggests several disguises, transforming himself into an Asgardian soldier, turning Thor into Sif(while retaining his voice), and transforming himself into Captain America. Later, near the end of the film, Loki is revealed to have taken Odin's form after faking his own death.
Vitriolic Best Buds: While not the best of friends anymore, Thor and Loki still act like this regardless, trading insults with each other. It crosses with Friendly Enemy
Wasn't That Fun?: After Jane Foster goes through the Bifröst for the first time, she quips, "We have to do that again!"
Volstagg:It would not be wise to have two Infinity Stones so close together. The Collector: (after they leave)One down, five to go.
Wham Shot: Odin shifting to Loki, revealing that he's somehow usurped the throne of Asgard and is once again ruling in Odin's place with Thor none the wiser.
When the Planets Align: The universe is about to witness the Convergence, an aligning of all Nine Realms that happens every five thousand years. When this occurs, passage between the realms is unmitigated, which is something Malekith is banking on in order to use the Aether to eliminate all existence in a single swoop.
When Things Spin, Science Happens: In Jane's lab there are a lot of gizmos that must do some technical scientific purpose that only Jane understands, but to laymen, they just spin.
World Gone Mad: As the Convergence begins forming rifts everywhere, a flock of birds fly into a portal then exit by flying up right in front of Selvig, Ian, and Darcy. Selvig merely comments:
Selvig: There's nothing more reassuring than realising the world is crazier than you are.
World of Badass: Asgard, Svartalfheim and Vanaheim are full of great warriors. Earth has the scientists who play a key part in Malekith's defeat.
The Wrongful Heir to the Throne: In his first film, Thor was unready to be king because he was too immature. In this film, he's matured to realize that he doesn't want to be king because he finds the sacrifices and ruthlessness required to be distasteful. Loki, on the other hand... When he claims that he was far better suited to be king than Thor, Odin doesn't disagree.
Year Outside, Hour Inside: For Jane, it was quick, but when she was teleported to another dimension and back, she had been missing for 5 hours. Jane was knocked out when the Aether entered her body and she could have simply been unconscious.
You're Insane!: Thor's reaction when Loki reveals his secret passage way out of Asgard, which involves driving a ship at high speeds through a crevice.
You're Not My Father: Loki furiously yells a variation of this when he and Frigga discuss Odin. Somewhat justified, as Loki had been disowned and would've been executed if it weren't for his mother's influence.