Many people credit 2002's Spider-Man with kicking off the current superhero movie craze, but X-Men came out two years before and was probably just as influential. At a time when comic book movies were not especially in vogue, it earned a very respectable $157 million at the domestic box office and another $139 million internationally. The film was also responsible for introducing these characters to general audiences who were not overly familiar with them.

Two sequels -- X-Men 2 and X-Men: The Last Stand -- followed. They, too, were box office blockbusters. After a hiatus of a few years, the widely-ridiculed spinoff X-Men Origins: Wolverine, was released. Although it made money, few people viewed it as a creative success. In a major attempt to course-correct, the franchise was rebooted in 2011 as a prequel trilogy. X-Men: First Class followed Professor X and Magneto as younger men. X-Men: Days of Future Past and X-Men: Apocalypse came shortly after. Yet another new installment, X-Men: Dark Phoenix, is slated for release in 2019.

All in all, those are eight cinematic releases bearing the words X-Men in their titles. With so many films and two sets of actors combining in the most recent installments, there were bound to be crazy behind-the-scenes stories. We've assembled twenty-five of the best. Each of these true tales sheds light onto the making of a cinematic series that has captured the imagination of moviegoers around the world. They will help you to understand why some of the X-Men movies were great, while others were lacking.

Here are 25 Crazy Facts Behind The Making Of The X-Men Movies.

Hugh Jackman was a last-minute replacement

Hugh Jackman as Wolverine

Wolverine is the role that made Hugh Jackman a star. Had circumstances been different, he might still be largely unknown and another actor might have become a household name. That's because someone else was originally supposed to play the part.

Actor Dougray Scott was cast as Wolverine, but had to step down after another movie he was making, Mission: Impossible 2, ran over schedule. For a time, it looked like things could still be arranged to get Scott to the X-Men set, but then he hurt his shoulder, slowing production down even more.

A replacement actor was required, with Jackman hired last minute. The rest is history.

Michael Fassbender was embarrassed by his performance

X-Men Days of Future Past Trailer - Erik Lehnsherr (Michael Fassbender)

Most fans agree that Michael Fassbender was an outstanding choice to play the young Erik Lensherr, better known as Magneto. In all three of the films in which he portrayed the character, his performance was praised.

In the case of Days of Future Past, the only person not happy with Michael Fassbender's work was the man himself.

During a fundraising event held at the Toronto International Film Festival in 2016, the audience was shown a clip from the movie in which Magneto goes into a rage. “I don’t actually like that performance there, to be honest,” Fassbender told the crowd. “I just think it’s me shouting.”

The original was rushed into production

Patrick Stewart and Ian McKellen in X-Men

X-Men was a hit with both critics and audiences. Truth be told, it's kind of a miracle that it turned out so well, given that the production was extremely rushed.

The movie was initially supposed to come out at Christmas in 2000. Then another big-budget Fox movie, the Steven Spielberg/Tom Cruise sci-fi adventure Minority Report, pushed its start date back, meaning it would never be done in time for its summer release date. Needing a summer blockbuster, the studio decided to move X-Men up to July, leaving only nine months to shoot the movie and do all the complicated post-production work.

Halle Berry's romance secret

During a 2017 interview with Entertainment Weekly, Halle Berry dropped a nugget of information that left X-Men fans reeling.

"Storm and Logan used to be lovers," she revealed. "It’s true. Storm and Logan had a thing."

She was referring to a deleted scene from Days of Future Past in which Logan kisses Storm goodbye right before traveling back into the past. Wanting to put some context to the moment, Berry and Hugh Jackman decided that their characters had once engaged in a fling that was "wonderful" until "Jean [Gray] came and messed that up."

Hugh Jackman injured a stunt performer

Hugh Jackman as Wolverine in X-Men Days of Future Past

Wolverine is famous for his dangerous claws, which he uses to slice and dice his enemies. During production of the first movie, real metal claws were used-- until someone got hurt.

Hugh Jackman was filming a choreographed fight sequence with Rebecca Romijn's stunt double. The actor was supposed to pretend to stab her in the arm, which she would move away as he swung. The stuntwoman's timing was off, causing the claws to strike her arm, cutting her and freaking out Jackman in the process. Fake claws were used thereafter.

The Last Stand was finished just two weeks before it hit theaters

There's nothing like coming in right under the wire to raise everybody's stress level, as the makers of X-Men: The Last Stand can attest to. They came scarily close to not getting done on time.

The attack on the Golden Gate Bridge -- which is one of the key scenes in the film -- required a lot of complicated special effects. 20th Century Fox scheduled the movie for release on the lucrative Memorial Day weekend, and had no intentions of changing that date. Under intense time pressures, the FX crew worked tirelessly, completing the final shot a mere two weeks before the film opened.

Jennifer Lawrence's makeup ordeal

Mystique makeup being applied

Jennifer Lawrence took over the role of Mystique from Rebecca Romijn for the second X-Men trilogy. She may not have realized what a grueling experience she was in for. Because of the character's distinct look, Lawrence had to have blue makeup applied to virtually her entire body.

It's a process that could take up to eight hours to accomplish.

In other words, it was a full work day before she ever even stepped in front of the camera. Adding to the discomfort was the need to stand around underdressed while the makeup was applied.

Olivia Munn passed on Deadpool to play Psylocke

Two very popular Marvel superhero movies almost looked a lot different. Olivia Munn had been under serious consideration for the role of Vanessa in Deadpool, but withdrew herself because she wanted to play a character who would get action scenes, as opposed to just being a love interest. Morena Baccarin played Vanessa instead.

Simon Kinberg, who produced both movies, told Collider that he was impressed with Munn and felt she'd be perfect in the X-Men universe. He recommended her two weeks later, and she was cast as Psylocke in X-Men: Apocalypse.

Wolverine replaced Kitty Pryde

Kitty-Pryde-Wolverine-X-Men-Days-Of-Future-Past smaller

Any time a book is adapted into a feature film, changes need to be made because movies work on slightly different principles. Sometimes the changes are small. In the case of X-Men: Days of Future Past, there was a major one.

In the book, Kitty Pryde is the one who goes back in time. For the film, it's Wolverine. Part of that was because Wolverine is the signature character in the cinematic franchise. Another reason is that Ellen Page had been cast as Kitty Pryde, and sending her back to the 1970s would, as producer Simon Kinberg put it, have made her "negative 20 years old." Wolverine is ageless, which got them around that problem.

Sophie Turner's Dark Phoenix preparations

The forthcoming X-Men adventure Dark Phoenix promises to be, as the title suggests, a little darker than previous installments in the franchise. To play the corrupted version of Jean Gray, actress Sophie Turner was given very specific reading material from director Simon Kinberg. She read up on mental health issues, specifically schizophrenia, to understand how they can affect an individual's state of mind and alter their behavior.

Turner utilized an online video designed to simulate what a schizophrenic person hears inside their head.

These tools helped shape her performance.

Famke Janssen wanted to play Jean Gray again

A promotional image of Jean Grey from X-Men: The Last Stand.

Watching some of the original X-Men cast members mix it up with the newer ones in the second wave of movies was a lot of fun. Not everyone was invited to the party, though.

Upon learning that Patrick Stewart and Ian McKellen were going to be featured in Days of Future Past, alongside their younger counterparts, Famke Janssen reached out to the filmmakers to see if there was any way the older Jean Gray could also be included. Janssen told Entertainment Weekly that the suggestion was, to her dismay, met with "total radio silence."

Anna Paquin didn't care that she was deleted from Days of Future Past

Anna Paquin returned to play Rogue in X-Men: Days of Future Past, so it was surprising when word got out that her performance hadn't made the final cut.

Many actors would be furious about such a fate.

Paquin really didn't care. The actress told Yahoo! Entertainment that she prefers to focus on her experience making movies rather than worrying how they'll come out. In the case of DOFP, "I got to hang out with my friends for five days in Montreal, and see people I’ve known for two decades and go play. Did it end up in the movie? No. Well, it was fun anyway.”

Hugh Jackman's cameo demands

Wolverine in X-Men First Class

Wolverine wasn't a character in X-Men: First Class, but the filmmakers wanted to find a way to squeeze him in, since Hugh Jackman had, by this point, become synonymous with the franchise. They devised a brief cameo in which Charles Xavier and Erik Lensherr meet him in bar, and he utters a profanity at them.

Jackman had two conditions under which he would agree to do the cameo, both of which were met. He wanted to be the only character to curse, and he wanted the studio to make a charitable contribution to his childrens' school.

James McAvoy shaved his head too early

James McCavoy as Professor X at funeral in X-Men Dark Phoenix

James McAvoy was familiar enough with Professor X to know that the leader of the X-Men is bald. When he was offered the role for X-Men: First Class, he did what he thought was the obvious thing to do -- he went and had his head shaved. That proved to be a bad idea.

Upon arriving to begin production on the movie, director Matthew Vaughn informed him that Professor X wouldn't be bald right away.

That was going to come later on. McAvoy therefore had to wear a wig in order to play the character in that film.

Oscar Isaac hated the promotional picture of Apocalypse

Alexandra Shipp, Oscar Isaac and Olivia Munn in X-Men: Apocalypse

When the first set photo of Oscar Isaac as Apocalypse was released, the public immediately began making fun of it. They thought he looked silly. Isaac himself was one of those who were unhappy, because he felt it was misleading.

The actor told Entertainment Weekly, "When you look at those things, you think that’s the representation of the character, and it was a shot from when we were coming out of a portal, and the portal light is purple and so suddenly everyone thinks that the character is purple which is not the case.”

X-Men Origins: Wolverine was leaked online before its release

Hollywood studios take a lot of precautions to prevent the piracy of their movies these days. That's due, in part, to X-Men Origins: Wolverine. An unfinished work print, with ten extra minutes of footage and unfinished special effects, was leaked online a month before it opened in theaters, presumably by someone with post-production access to it.

Experts estimated that the online availability of Wolverine cost it tens of millions of dollars at the box office.

The leak created panic in the halls of 20th Century Fox, because people could now essentially see the big summer blockbuster for free.

Jennifer Lawrence changed her mind about playing Mystique again

Mystique prepares to face Jean Grey in X-Men: Dark Phoenix.

Jennifer Lawrence had to endure an arduous makeup process every time she played Mystique. Since she portrayed the character in three different films, that meant a lot of time in the makeup chair. For that reason, it really wasn't a surprise when she announced that she was done with it all after X-Men: Apocalypse.

The departure didn't last long. After some time away, Lawrence made an about-face, agreeing to resume the role once more for the upcoming X-Men: Dark Phoenix. The actress explained her decision to Digital Spy, saying, "I felt like I owed it to the fans, and I owed it to the character to follow her journey."

Halle Berry never replied to the new Storm

Alexandra Shipp X-Men Apocalypse

Halle Berry played Storm in the original X-Men movies. By the second wave of films, a younger actress was needed for the role. Alexandra Shipp, who was best known from the Nickelodeon show House of Anubis, took it over.

Since she was inheriting the part from an Oscar-winning star, Shipp emailed Berry for advice, but never got a reply.

Despite the snub, Shipp was unfazed. “I reached out to her,” she stated in an interview with Yahoo! Entertainment. “You know, Halle’s got her show [Extant] and her family and stuff. So I understand, she’s got her thing going on."

Lady Gaga as Dazzler?

Lady Gaga looks on in American Horror Story

Whenever a new actor was announced to play one of the X-Men, it made news in the entertainment media. For that reason, director Bryan Singer thought it would be funny to play a little April Fool's joke on the fans.

In 2013, he used his social media accounts to say that Lady Gaga would be joining the team to play the Dazzler.

For those uninitiated, Dazzler was created in 1980 as a collaboration between Marvel Comics and Casablanca Records to capitalize on the disco craze. Her mutant ability was being able to turn musical vibrations into powerful beams of energy. She is largely considered cheesy by the majority of fans.

Trouble in New Zealand

X-Men Origins: Wolverine filmed in New Zealand, and it didn't take long for the production to get in trouble with local authorities. The financially-struggling Queenstown Fun Center, which included a large ice rink, granted them permission to use the facility to store equipment.

Among the things being stored there, however, were explosives. This went against the center's lease with the local district council, the members of which were not happy about the potential danger of this situation. The Wolverine team had to promptly find a new place to keep the explosives.