• When Beast meets Leech, a close-up of Beast's face as he remarks on Leech's power reveals the net-like tape used to attach the blue fur to his face.
• When Wolverine shows Jean Scott's glasses when he is trying to control her, a close-up of his hand reveals a small cut on one of his fingers. In the X-Men universe, Wolverine has healing powers that prevent him from having any cuts on his body for any significant length of time.
• While Jean Grey was tearing off Wolverine's skin, in the last and the biggest tear off, despite Wolverine has restored completely, when Jean Grey starts to tear off, the wounds previously occurred have healed in one frame, less than a millisecond.
• Time of day during the final battle sequence. The first pan over the bridge from southeast looking north, is clearly midday as the shadow of the bridge is almost directly underneath it. When Magneto first walks onto the Golden Gate bridge it is close to sunset, and the shadowing is very inconsistent, sometimes sharp from direct sunlight, sometimes not. By the time they move the bridge and drops it onto the island, and lowers himself to the bridge, and all the mutants move forward, it is suddenly dark. In the DVD commentary, everyone acknowledges it, but says "Hopefully you're into the movie enough . . ." The whole battle is then shown as taking place in the dark.
• When Wolverine leaves on the motorcycle from the school and goes to the woods looking for Jean, to Magneto's hide-out, he is wearing a brown leather jacket. But, once in the woods, he senses something, the camera pans down as he extends his claws. Although the DVD Commentary from the Writers & Director mention it and jokingly say "He has a mutant power here, the ability to lose his jacket. He has a jacket here, if you look at his sleeve . . . and now, no jacket." This is because right after that he is shown in nothing but the white wife-beater style t-shirt. But if you look at it in slow-motion, and see in subsequent shots, it is actually his watch. In some shots, his jacket hangs as low or lower than the sleeve and if he was wearing it, we would most likely have seen the front part of the jacket against his jeans in that shot.
• In the woods at Magneto's hide-out, Wolverine is attacked by the mutant Spike. When he kills Spike, he has two spikes in his stomach on either side of his belly button. The wounds heal, and you see the holes in the wife-beater style t-shirt he is wearing, but in the rest of these scenes, the holes are gone.
• When Dr. Kavita Rao prepares The Cure injection for Angel, at first, the needle clearly doesn't have the plastic protective cap on, then she takes it off in the next shot.
• In the scenes of traffic on the Golden Gate Bridge, there are no yellow lane markers separating the northbound and southbound lanes. They are used to adjust the number of lanes in each direction, and they're always present on the bridge.
• On several occasions, the line where Mystique's blue makeup ends around her mouth is easily visible.
• When Scott rides to the lake, he is on a Harley-Davidson V-Rod, but the audio used for the engine noise is from a regular V-Twin Harley engine. The V-Rod's engine sounds more like a car than a typical Harley.
• Wires are visible during second "Fastball Special", where Colossus throws Wolverine towards Magneto.
• When Professor Xavier and Magneto enter Jean Grey's old house and find her sitting on a chair, items in the room are levitated around her. When the items drop, the bookcase over her right shoulder hits the ground and all the books fall off, the lamp on top remains on. In a later shot the books are back in the book case and the lamp is on the floor.
• The word "too" is misspelled as "to" in the caption "The not to distant future". (Corrected on DVD version)
• At the final battle, when the X-men are lined up, Wolverine is too far forward from the light pole to just swings back and cut (as he does) so it falls onto the attacking mutants, then as Wolverine is fighting off more mutants, the light pole can be seen right behind him still up.
• When Magneto drops the bridge, he flies above it to avoid the impact, which is hard enough to crush several buildings on the island. But none of the Brotherhood or cars on the bridge seem to have been disturbed by falling 100 feet to the ground.
• At the end scene with Jean and Wolverine, there is a shot of him from behind, and his beard makeup is hanging slightly loose from his cheek.
• When Juggernaut is inside of the building attempting to find Leech and destroy him, Kitty pulls him into the floor. Juggernaut's power is that when he has momentum nothing can stand in his way, yet he later destroys the floor holding him just by moving his arms up, he could never have gained momentum because he couldn't move his arms. However, Juggernaut's legs could have been dangling THROUGH the floor. If he wiggled them, that would be all the momentum he would need to break free.
• After Magneto and his Brotherhood leave Jean's house after the fight, Wolverine and Storm are running to find Professor Xavier. In the shot just before they burst into the room he was in, Wolverine's claws are out. In the next shot he falls to his knees and his claws are in. There is no "SINKT!" metallic noise in between.
• When Wolverine arrives at Magneto's camp, he is attacked by Spike. It appears Spike is close behind due to the time it takes for him to throw the spike and when it is passing Wolverine. Wolverine is hit, and he pulls one out of his shoulder and appears to throw it into Spike's leg as Spike comes over the big felled tree. Another mutant comes over the tree after him, (with a gun, which was also an issue with the movie makers - why would mutants need guns?) and Wolverine fights with him and others, slashing his way through the forest, and then appears to arrive where Spike fell after being hit and appears to kill him - and that victim has the EXACT tattoos, clothing and hat of Spike, but appears to be wearing something from the elbow, to hand, and apparently had a shotgun. Then, Wolverine is being attacked again by Spike from a distance, but Spike had been following him closely earlier, so why would he be so far away? They get closer and closer and Wolverine kills him, and you don't see a spike in Spike's leg.
• Joël Einhorn's name is spelled as Joel ëinhorn in the end credits of the movie.
• During the final battle, Beast and Wolverine spot unused 'cure' darts in a gun cartridge. At first there are four darts, then when they look again, there are three. Later when the darts are used against Magneto, there are four again.
• After Wolverine stabs Jean, the scene shows that there are no cars missing on the bridge, but that isn't possible because Magneto threw dozens of them at the troops.
• After Wolverine stabs Jean and the camera pans upwards to view the bridge, all of the cars have their headlights on, which is impossible because it was broad daylight when the owners abandoned them earlier.
• • When Wolverine confronts Jean/Phoenix, her aura of strength destroys his clothing. Yet mysteriously, the "pants" region of his clothing is not destroyed. His entire suit is, presumably, the same material, so there is no reason one part of his clothing should remain while the other parts are destroyed. However, one must realize that the creators were shooting for a pg-13 movie, and therefore, Wolverine's pants must stay on.
• The "Tracking Mutations" issue of Scientific American that Hank McCoy/Beast is reading in his office while hanging from the ceiling was not a fake prop; the magazine actually had that cover story in October of 2005.
• Angel's wings were initially too heavy for Ben Foster, and were remade from foam.
• Patrick Stewart's "de-aged" effect in the opening scene was based on publicity photos from the first season of "Star Trek: The Next Generation" (1987).
• Halle Berry had initially decided not to reprise her role as Storm for this film, citing lack of character development in the previous two installments and a tense relationship with director Bryan Singer. However, after Singer's departure and suffering a major box-office flop with Catwoman (2004), Berry agreed to return on the condition that her role be expanded. Consequently, in this film Storm serves as leader of the X-Men, which is keeping with the comics since she served as team leader for a time in Xavier's absence.
• When Bryan Singer was still set to direct, he intended the Dark Phoenix storyline as the sole focus of the film. He also intended to feature the villain Emma Frost/White Queen as a major character, with the role intended for Sigourney Weaver. With Singer's departure, the character of Emma Frost was dropped, and the Dark Phoenix story was relegated to a subplot in favor of the "cure" storyline. He also planned on introducing long time fan favorite Gambit into the film, to serve as both the new recruit as well as a romantic rival of Iceman's for Rogue's affection. For the part, Singer had planned on casting Channing Tatum. However, once he left, the script was changed, and Gambit was reduced to a minor cameo, then ultimately dropped from the script.
• The characters Phat and Spike (both from the X-Statix comic book) make cameo appearances.
• Cain Marko's line "Don't you know who I am? I'm the Juggernaut, bitch" was inspired by a popular web parody film that made use of scenes from "X-Men The Animated Series." Throughout the parody , the Juggernaut character repeatedly says, "I'm the Juggernaut, bitch." According to the Wikipedia, Brett Ratner even has a link to this parody on his own website. (Whether or not the parody itself was inspired by a mis-heard line from an old X-Men video game is irrelevant to film's usage of this line, since it's clearly an homage to the web parody)
• Summer Glau auditioned for the role of Kitty Pryde. She looked to Joss Whedon, who gave her a part in "Firefly" (2002) and Serenity (2005), for advice because she knew he was a big X-Men fan, unaware that he had written the "Astonishing X-Men" comic book for Marvel, featuring the storyline about the mutant cure. Her audition script turned out to be pages from issue 5 of Joss Whedon's Astonishing X-Men book.
• Ian McKellen (Eric Lensherr/Magneto) and Patrick Stewart (Professor Charles Xavier) had 20 years shaved off their features for the opening sequence. The filmmakers used digital technology to match current features to those in old photos.
• The number on Jean's mail box is 1769.
• The idea of a cure developed by Dr. Kavita Rao, Beast's interest in it, and the prominent roles played by Kitty Pryde and Colossus, were inspired by Joss Whedon's story "Gifted" which took place in the first six issues of "Astonishing X-Men".
• The last scene with Magneto in Golden Gate park was actually filmed in London. It was originally meant to have Mystique sitting across from him, to imply that she had been on his side throughout the whole movie. Rebecca Romijn, however, was unavailable due to a television series (Pepper Dennis) she was filming at the time.
• Body count: 56
• WILHELM SCREAM: during the final battle when the mutant hanging underneath the scaffolding pulls the Cure dart out of his neck and becomes human again, falling to his death.
• Mike Vogel was up for the role of Angel, but could not take the part because scheduling conflicted with Poseidon (2006).
• Jed Bernard auditioned for the role of Warren Worthington/Angel.
• Nick Stahl was considered for the part of Warren Worthington/Angel.
• To create the Golden Gate Bridge sequence, the art department built a full-scale section of the bridge that was about the size of a basketball court (94 feet). The rest of the bridge and the background was digital.
• The character Callisto has been given entirely new powers in the movie. In the comics, Callisto has merely enhanced strength, speed, and agility, and her main power was the ability to instantly calculate the tactical solution to any problem. Her powers in the movie of super speed and the ability to detect mutants seem to be a combination of Quicksilver (Magneto's son) and either her comic book ally Caliban or Sage, both of whom can detect mutants.
• The Danger Room scene was a mock up of the story "Days of Future Past", where mutant-hunting Sentinels tracked mutants in a war-torn world. Specifically, it is the portion of the story that takes place in the "not too distant future" of 2013 (which at the time the original comic was published would have been over 30 years in the future) that is reproduced.
• The character Arclight was originally intended to be a character new in the comics named Stacy X. She was a mutant prostitute with the ability to control people by producing pheromones. This was originally part of Matthew Vaughn's production.
• The character Leech appears in the comic as a small green boy, rather than a normal looking human child.
• The bridge scene is based on the scene in "New X-Men" #147 involving the Manhattan and Brooklyn bridges rather than the Golden Gate Bridge.
• The Sentinels make a cameo appearance in the scene where Colossus throws Wolverine into the air, then a giant robot head hits the ground with Wolverine behind it.
• Instead of high-dollar CGI to create Colossus' transformation, a reflective form-fitting bodysuit was created for and worn by Daniel Cudmore in some scenes.
• The Fastball Special, when Colossus throws Wolverine, finally makes it into the movie. It has been a big part of the comic for some time, but Brett Ratner specifically studied John Cassaday's interpretation in 2004's "Astonishing X-Men" #6.
• The Juggernaut used in the film is based on his "Ultimate X-Men" version, where he is a mutant, instead of gaining his powers through the mystical, South Korean gem of Kytorakk. He is also the step-brother of Charles Xavier.
• Cyclops' sunglasses are Oakley's "Penny" model, a limited edition sunglass.
• Matthew Vaughan was originally hired to direct the film. Six weeks before filming was to begin, Vaughan left the film for personal reasons. Brett Ratner replaced him and the film stayed on track.
• Maggie Grace was originally cast as Kitty Pryde but was replaced with Ellen Page after the filmmakers discovered that she was too old for the role.
• The film's premise was a combination of two graphic novels. First, the premise of the cure as well as Dr. Rao was taken from Joss Whedon's Astonishing X-Men novel, Gifted. The other one was based on Chris Claremont and John Byrne's "The Dark Phoenix Saga" (Uncanny X-Men #129-137).
• Bryan Singer was in the middle of a three-picture deal made with Fox beginning with X2, and keen to make X-Men 3, but he and Fox were unable to come to terms. During this time, Warner offered him the chance to direct Superman Returns (2006) immediately. Singer informed Fox that he was going to take this opportunity and would still like to return to direct X-Men 3. As the consequence, his deal was terminated and Matthew Vaughn briefly joined the production before he backed out. Brett Ratner was the finalist for the director's role for the first X-Men movie, having experience of making a successful film out of a rushed production with 'Rush Hour'.
• Both Rebecca Romijn (Mystique) and James Marsden's (Cyclops) roles were reduced substantially when the film was rushed into production and the two cast members had prior scheduling conflicts.
• Ellen Page initially turned down the role of Kitty Pryde. Brett Ratner had to call her personally and have her read the script. She then agreed.
• Backflip from tree during Logan's/Wolverine's fight with mutants in the forest was made by Hugh Jackman, not a stunt double. Stunt of Wolverine being thrown through forest by Magneto was also performed by Hugh Jackman himself. (as stated in DVD commentary track)
• The character Trask is Bolivar Trask. In the comics, he creates the mutant-hunting Sentinels, similar to the robot Wolverine beheads in the opening scene.
• This is the first film in the series to feature the original line-up of the X-Men from the comics: Professor X, Cyclops, Jean Grey (though originally as Marvel Girl, not Phoenix), Iceman, Beast (Dr. Hank McCoy, though the character briefly appeared on TV in the second film sans blue fur), and Angel (Warren Worthington III). Most of the rest of the major characters joined the team in Giant-Size X-Men #1, almost a hundred issues later: Storm, Wolverine (though he had previously appeared in two Hulk comics), Collossus, and Nightcrawler (along with Banshee, Thunderbird, and Sunfire who do not appear in the movie, though Banshee's daughter Siryn makes a cameo in the second film). Kitty Pryde joined the team after the "Dark Phoenix Saga". Rogue would not appear until a few years later, and then it was as a member of Mystique's Brotherhood of Evil Mutants, which also included Pyro, Blob, Avalanche and Destiny.
• Cameo: [Stan Lee] man holding water hose in beginning of movie.
• Rebecca Romijn and Sam Elliot have both played Major & Supporting roles as different characters throughout the Marvel Universe. Sam Elliot played a major role as General Ross in Hulk, and a supporting role as the Caretaker in Ghostrider. Rebecca Romijn had a major role as Mystique in all 3 X-Men movies, and played a supporting role as Joan (Frank's neighbor) in The Punisher, which Ben Foster, who played Warren Worthington in X3, Was also a supporting actor in as Dave (Frank's Neighbor).
• Hugh Jackman, Halle Berry & Vinnie Jones had all acted together in the 2001 movie 'Swordfish"
• Has the biggest Memorial Day boy-office opening ever, until the record was beaten by Pirates of the Caribbean: At World's End (2007).
• Famke Janssen did much research on schizophrenia in order to make her performance with Hugh Jackman in the medical lab more realistic.
• The final scene of Magneto, in which he is able to use his powers to move the chess piece, as well as the coda after the credits where Professor X speaks to Moira MacTaggert, were not in the script, but secretly added during filming. Both Ian McKellen and Patrick Stewart admitted that even they, the actors, didn't know if the scenes would appear in the final edit until they saw the finished film.