When Wolverine complains about their outfits, Cyclops asks him if he'd prefer yellow spandex. This in-joke refers to the fact that one of Wolverine's costumes in the X-Men comics is predominantly yellow.
Stan Lee (X-Men creator and executive producer) is seen as a man near a hot dog stand on the beach when Senator Kelly comes out of the water.
George Buza, the trucker, portrayed the voice of Beast in the "X-Men" animated series.
Hugh Jackman took cold showers to help him create the character Wolverine's trademark "berserk edge."
More than 700 individual claw blades, made of hard plastic, were used by Hugh Jackman and his four stunt doubles.
Mystique's costume consisted of blue dye and a handful of small, strategically placed plastic scales. When in full Mystique makeup, about 60 percent of Rebecca Romijn-stamos' body was covered in prostheses.
After a defeated Storm re-enters the fight, Toad complains, "Don't you people ever die?" This is an in-joke since, in the comics, almost all of the characters featured have "died" at least once, then come back.
Most of the eye effects were done by using special contact lenses that the actors found very uncomfortable to wear. Rebecca Romijn-stamos (Mystique) could only wear her lenses for an hour at a time and had only 10% vision. Halle Berry (Storm) was supposed to wear opaque white lenses for the scenes where she uses her weather-control powers. However, she found the lenses unbearable, so her eye effects had to be done entirely through CGI.
In the comic book canon, Rogue's name is unknown.
Many facts in the X-Men comic book universe were lost on the way to the screen. For instance, Storm is claustrophobic (and would not be able to navigate in a narrow elevator shaft), and Wolverine is only supposed to be 5'3".
Colossus, another comic-book X-Men character, appears briefly in this film, in a park scene. He's shown painting, which fits with the comic Colossus' love of art.
Famke Janssen played a self-described mutant with limited telepathy whom Patrick Stewart attempted to help in the "Star Trek: The Next Generation" episode "The Perfect Mate."
Ten Wolverine costumes were built out of thick leather and PVC and were designed to take a beating. All of them were destroyed to some extent during filming.
Along with Cyclops, Jean Grey, Storm, and Wolverine, a blue-furred character called The Beast was going to be included in the X-Men's roster. However, because the make-up for the character would be extensive, the character was cut and his scientist persona was grafted onto Jean Grey, who became "Doctor" Jean Grey.
Many of the X-Men from the comics who don't have major roles in the film still appear as minor characters in the school. Among them are: Jubilee, the Asian-American girl wearing a yellow jacket, hoop earrings with sunglasses above her forehead (seen in Professor X's class room when Wolverine first enters, and again sitting next to Rogue in Storm's class), Shadowcat, also known as Kitty Pryde (she walks through the door), and Iceman, aka Bobby (the one who makes the iceball for Rogue).
The "X" in the 20th Century Fox logo at the beginning of the film lingers and brightens as the logo fades out.
In the comic, Mystique isn't a fighter and could never hold her own against Wolverine. Same with The Toad.
After knocking Storm down an elevator shaft, Ray Park (Toad) kicks away the bar that was holding the elevator doors open, grabs the bar, spins it over his head and then holds it in an attack posture in the same way he does with the double-ended lightsaber as Darth Maul in Star Wars: Episode I (1999).