* ActingForTwo: Of a sort. The 'Grace' persona that Mystique uses to seduce the security guard is just Rebecca Romijn out of make-up. She's billed for playing Mystique and Grace in the end credits.
* ActorInspiredElement: Both Creator/IanMcKellen (who is gay) and Creator/BryanSinger (bisexual) worked with the screenwriters to make the scene in which Bobby Drake tells his parents he is a mutant, to look more like a "coming-out" scene.
* CaliforniaDoubling: Hatley Castle in Victoria, British Columbia was used for the exterior and most of the interior of Xavier's school.
* CastTheExpert:
** Professional mimes were hired for the scenes where Xavier freezes people in the room - naturally because they'd be able to hold still for longer than regular extras.
** Creator/AlanCumming speaks fluent German and was cast as Nightcrawler for this reason.
* CowboyBebopAtHisComputer:
** In a ridiculously inaccurate negative review by Stephen Hunter of ''The Washington Post'' it quickly became clear that he did not bother to watch the movie, or was distracted for most of its length. At one point, he said that Rogue had the power to ''reverse time'', even going so far as to call her "the Mistress of Rewind." He was apparently confused by the scenes in which she extinguishes flames (using Pyro's power) and makes Wolverine's wounds reappear (he let her borrow his HealingFactor).
** A review in the ''Irish Times'' complained that a character who had been killed in the first film was somehow alive in the second... except he wasn't: Mystique the shapeshifter had taken his place. This was not only pointed out explicitly in the first film (for those viewers too sleepy to notice the characteristic flash of yellow eyes) but was a ''pivotal plot point'' in the second, which makes you wonder if the reviewer actually bothered to watch the film.
** One ''TIME'' magazine profile of Creator/AlanCumming described him as playing a "mutant villain". As in, Nightcrawler. Granted, it's an easy mistake to make if you only read the Website/{{Wikipedia}} article on the movie, in which the first sentence of the plot summary reads, "Nightcrawler, a teleporting mutant, attempts to assassinate the President of the United States," and (as of this writing) doesn't actually explain that he was BrainwashedAndCrazy even if you read on from there. Perhaps they should have bypassed the question of which side he was on and just pointed out that he spent up to nine hours getting the makeup put on him, which would be the only interesting part to someone who hadn't seen the movie anyway.
* CreatorBacklash: Alan Cumming had a miserable time on the set, describing it as "dangerous" and "abusive" due to Bryan Singer's drug problems and hostile behaviour. The studio failed to intervene and he ended up gaining a lot of weight due to binge eating and drinking whenever he got home because of how upset he was. This was the reason he didn't return for ''Film/XMenTheLastStand''.
* CreatorChosenCasting:
** Creator/BryanSinger only had Creator/BrianCox in mind for Col. Stryker, having been a fan of the actor ever since he saw him in ''Film/{{Manhunter}}''.
** Creator/AlanCumming was always Singer's first choice for Nightcrawler, but he initially couldn't accept due to a scheduling conflict. The film spent so long in development that he became available.
* DeletedRole: The film was meant to feature brief cameos from Beast and ComicBook/{{Gambit}} during the brainwashed Professor X's telepathic attack on the mutants, which would have caused their powers to flare involuntarily. The Gambit piece was shot with Simon Sherr playing him, but it was cut from the film. The characters would later appear in ''Film/XMenTheLastStand'' and ''Film/XMenOriginsWolverine'' (with Taylor Kitsch replacing Sherr), respectively.
* DeletedScene: [[DeletedScene/XMenFilmSeries See here]].
* DisownedAdaptation: Creator/ChrisClaremont doesn't necessarily hate the film, but over the years has come to view it as a poor adaptation of ''ComicBook/GodLovesManKills'' due to all the changes to the original storyline.
* DyeingForYourArt: Creator/HughJackman was given a nutritionist to get in shape for his role as Wolverine, and gained twenty pounds. On the make-up front, Creator/AlanCumming joined Rebecca Romijn in the long and arduous process of becoming a blue Mutant.
* FakeAmerican: The Scottish Creator/BrianCox as Stryker.
* FakeNationality:
** The German Nightcrawler is played by Scotsman Creator/AlanCumming.
** Australian Creator/HughJackman once again plays the Canadian Wolverine.
* MakingUseOfTheTwin:
** A hilarious variation. Creator/HughJackman's ''sister'' visited the set one day. As a joke, she was made up like Wolverine and walked around the set in costume. She even shot some scenes. Creator/BryanSinger didn't realise the difference at first, merely wondering why Hugh was acting so strangely that day.
** A straight example when Mystique impersonates the janitor in Stryker's office. She walks by the real one while in disguise. Identical twins were used to achieve the shot.
* TheMerch: The Mazda RX-8 X-Men Car, a limited edition Mazda RX-8 based on the Mazda RX-8 in the movie. Available in "Mutant Blue" with an X-shaped grille and an enlarged X on the nameplate.
* NoStuntDouble: Creator/AnnaPaquin did the wirework for Rogue getting sucked out of the Blackbird herself.
* OnSetInjury: Creator/HughJackman was injured doing a stunt in the X-Jet that caused him to bleed.
* OrphanedReference: A planned idea was for Jean to be rendered blind after her fight with the brainwashed Cyclops. It was filmed as such but dropped later in production. If you pay close attention when Wolverine shuts the dam door to save them from the water, Jean is the only one not looking at him.
* TheOtherDarrin: Creator/AaronStanford, Kea Wong and Katie Stuart replaced Alex Burton, Katrina Florence and Sumela Kay as Pyro, Jubilee and Shadowcat respectively. The replacement of Alex Burton in particular drew some press, as he filed a civil lawsuit against three of Bryan Singer's friends for alleged sexual assault during the production of the first film.
* RealLifeWritesTheHairstyle: Creator/HughJackman had hair extensions for ''Film/VanHelsing''. Then he went and filmed the reshot ending and his hair is clearly bigger.
* ReferencedBy: The [[https://www.youtube.com/watch?v=UngE0qn3VRY&feature=youtu.be&t=2m37s "What If Wes Anderson Directed X-Men?"]] video contains a joke where Wolverine is identified as the art teacher at Xavier's school.
-->'''Iceman''': ''(watches as Wolverine dramatically runs towards a Sentinel)'' Who was that?!
-->'''Angel''': I think he's the art teacher!
* RefittedForSequel: The bathroom set was originally built for a flashback scene Cyclops discovering his powers, that was left before being shot. Also, a scene similar to what they'd intended turns up in ''Film/XMenOriginsWolverine'' and later ''Film/XMenApocalypse''.
* TroubledProduction: Filming wasn't nearly as troubled as the first film, but Creator/BryanSinger's onset attitude caused problems again.
** Late in production, producer Tom [=DeSanto=] grew very concerned about Singer's increasingly erratic behavior. When [=DeSanto=] came to the set one day and found the director, along with several crew members, apparently under the heavy influence of narcotics, he tried to halt production out of fear someone could get hurt. This resulted in a long, loud argument between the two of them that almost turned physical at many points.
** And indeed someone did get hurt. While filming a scene on the X Jet, Singer decided to skip ahead to a scene scheduled for the following day that required a stunt from Creator/HughJackman. Because it wasn't supposed to have been filmed that day, the stunt coordinator was not present and Jackman ended up injured and bleeding. Ralph Winter then ordered production shut down, which led the studio to overrule him and summon [=DeSanto=] back to LA.
** The cast, still in costume, responded by confronting Singer in his trailer and threatening to quit if [=DeSanto=] left. It was during this confrontation that Creator/HalleBerry reportedly told Singer to "kiss my black ass", a story often repeated but given different contexts; according to Creator/AlanCumming, Berry had been telling Singer about several former colleagues who had been similarly addicted to drugs before turning their lives around, to which Singer accused her of being "full of shit" and threatened to fire her or anyone else who broached the topic of his addictions, leading to her angrily storming out. Singer has through his reps denied any of this.
* WagTheDirector: By shooting time for the film, Creator/HalleBerry [[UsefulNotes/AcademyAward had more clout]], and used it to give herself a bigger part (and more money) in the movie, and lo, here comes her conversations with Nightcrawler and use of powers against the missiles.
* WhatCouldHaveBeen:
** Creator/NeilPatrickHarris and Creator/EthanEmbry auditioned for the part of [[ComicBook/{{Nightcrawler}} Kurt Wagner]] before Creator/AlanCumming was cast.
** Early on in the film's production, Creator/ShaquilleONeal lobbied to play the part of Bishop. Due to Creator/DavidHayter not having any familiarity with the character, Shaq didn't get the part. The character would later debut in ''Days of Future Past'', played by Creator/OmarSy.
** Creator/RayPark was going to return as a brainwashed Toad and get into a fight with Nightcrawler while the latter and Storm were trying to rescue the mutant kids. However, schedule conflicts prevented this, and as a result, the set that was built just for this scene was not used.
** Comicbook/{{Sabretooth}} was planned to return, this time as Stryker's bodyguard. However, the part was rewritten into Anne Reynolds, Stryker's bodyguard from the comics, who would have been granted Lady Deathstrike's mutant powers and adamantium claws for this film. Her role was then filled by Lady Deathstrike herself and given longer fight scenes so that the movie would have more action.
** Originally, ComicBook/{{Magneto}} would have rescued Professor X from Dark Cerebro and escaped with the other X-Men instead of trying to KillAllHumans, but this was rewritten to keep Magneto's ruthlessness. Also, initially he was the one executing the plan by fixing Dark Cerebro, not Mystique deceiving Jason.
** Pyro attacking the police cars was planned to end with Storm putting out the fires with a sudden rainfall. The budget didn't allow for this, so they had Rogue drain his powers and put the fires out herself.
** The scene in which Storm and Nightcrawler rescue Xavier was going to be much longer and quite more dramatic. Jason would have trapped them in trippy hallucinations, which they escaped only because Dark Cerebro was falling apart and it disrupted his illusions. They would have next talked Xavier into realizing the ruse, and the professor would have engaged Jason in a psychic battle, mind-raping him and finally defeating him with Storm's help. Jason would have then shown remorse on his face before being sent into the abyss by a falling girder, after which the three X-Men escaped narrowly.
** Hank was supposed to be shown turning into Beast when the "destroy all Mutants" plan was launched, showing that his human-looking self was induced through serums. Other mutants who would have been shown affected by the plan were Marrow and Gambit. (In another cameo-related affair, a young Multiple Man was going to appear at the beginning of the film in a scene with Siryn.)
** Several versions of the script had Jean surviving the film and returning with the others. This was kept in the official novelization.
** Angel was planned to appear as a student at the Xavier Institute. He would've been one of the teens taken captive during the raid on the school, and Stryker would've forcibly transformed him into Archangel at his lab. This subplot was cut, but the X-rays of Angel's wings can still be seen during the scenes in Stryker's facility.
** The Danger Room was going to feature in the film. When Scott, Jean and Storm are away, Wolverine would take some of the students for a workout in the room. A sneak peak of how it would look was even in the teaser trailer. But the budget got cut down, and the scene had to be scrapped.
** Many of Cyclops' scenes were cut from the final film. Aside from the extended deleted scene mentioned above, he also had a longer fight scene with Deathstrike.
** A planned idea was for Jean to be rendered blind after her fight with the brainwashed Cyclops. It was filmed as such but dropped later in production. If you pay close attention when Wolverine shuts the dam door to save them from the water, Jean is the only one not looking at him.
** Nick Fury was planned to be in this film but was removed from the script.
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