To prepare for the role, Hugh Jackman contacted Dwayne Johnson for advice on bulking up for the movie. Johnson suggested Jackman could gain a pound a week over six months (24 weeks) by eating 6,000 calories a day of "an awful lot of chicken, steak and brown rice."
Hugh Jackman said that for his shirtless scenes in the film, he wanted to look "as ripped and cut as possible". So he adopted a dehydration diet (used in bodybuilding) where he did not consume any liquid for 36 hours before filming his shirtless shots. He said it made him feel "headachy" and faint but he was pleased with the results as dehydrating tightens everything up and gave him the exaggerated muscle definition and vascularity that he wanted to show in his shirtless scenes.
Famke Janssen filmed her Jean Gray cameo in three days. Hugh Jackman said, "There's no doubt that the most important relationship in his life is - we've seen through the movies - is his relationship with Jean Grey. Yes, we saw her die at the end of X-Men: The Last Stand (2006), but in this movie, she has a presence which I think is vital to the movie, particularly for him confronting the most difficult thing within himself."
Hugh Jackman said that with this film, he finally achieved the physique that he always envisioned in his mind that Wolverine should have. He said that for some reason, on each of his 5 prior takes at the character, he felt that he never had enough time to get in shape; for this film he finally had enough time, and got his body exactly the way he wanted it to look. Co-star Will Yun Lee also said that it was Jackman's best physique for the role of Wolverine.
Hugh Jackman is a self-confessed fan of the Chris Claremont-Frank Miller "Wolverine" comic (1982), especially the Japanese saga: "There are so many areas of that Japanese story. I love the idea of this kind of anarchic character, the outsider, being in this world full of honor and tradition and customs; someone who's really anti-all of that, and trying to negotiate his own way. The idea of the samurai too, and the tradition there - it's really great. In the comic book he gets his ass kicked by a couple of samurai - not even mutants."
According to Hugh Jackman, Wolverine being surrounded by death while being unable to die due to his healing factor is a major theme in the film: "He realizes everyone he loves dies, and his whole life is full of pain. So it's better that he just escapes. He can't die really. He just wants to get away from everything."
The film was scheduled to be released in Japan in mid-September, more than a month after its worldwide release. This was to avoid insensitive screenings during the early August anniversaries of the nuclear attacks on Hiroshima and Nagasaki (the film itself opens with the Nagasaki bombing).
Guillermo del Toro expressed interest in directing, being a fan of the Japanese saga in the "Wolverine" comics. He met with James Gianopulos and Hugh Jackman about directing the film, but ultimately decided he did not wish to spend 2-3 years of his life working on the film.
For the bullet train fight, the actors and stunt performers filmed on wires above a set piece surrounded by a green-screen. The moving background came from filming on an elevated freeway in Tokyo. The visual effects artists got the background from filming with a rig and eight Red Epic cameras angled at 45 degrees. Filming at 60 km/h, the footage was then sped up to 300 km/h.
Hugh Jackman confirmed on having discussions with director James Mangold about test screening a PG-13 rated cut and an R rated cut, but did not comment on filming sequences for them. Although the film was confirmed to be rated PG-13 via a tweet from James Mangold saying "it's PG-13, but don't worry, it ain't Bambi (1942)." An unrated/extended cut is confirmed exclusively for the 3D BLU-RAY release.
According to James Mangold, the film had started out as a prequel to X-Men (2000), but later he decided to make it a sequel to X-Men: The Last Stand (2006): "I wanted to tell the story without the burden of handing it off to a film that already exists and having to conform to it. The ideas of immortality reign very heavily in this story, and the burden of immortality weighs heavily on Logan. For me that's such an interesting part of Logan's character that it is nearly impossible to explore in a prequel."
Darren Aronofsky was originally set to direct and worked on the project for six months before departing, citing the long overseas shoot would prevent him from seeing his family (he had just separated from Rachel Weisz, the mother of his child). During his time attached to the film, he rewrote the screenplay by Christopher McQuarrie and it is speculated that the real reason for his departure was the studio's unwillingness to approve his draft - which aimed for a hard 'R' rating due to heavy sexual content and brutal violence.
In an interview with MTV News' Josh Horowitz, promoting The Wolverine (2013), Hugh Jackman admits that when he initially took on the role as Wolverine he studied wolves to develop his character, since he thought that Woleverine must allude to wolves. It took Bryan Singer to enlighten him for Hugh to realize that a wolverine is actually an own animal-species.
According to James Mangold, this film is a sequel to X-Men: The Last Stand (2006) ("Jean Grey is gone and most of the X-Men are disbanded, so there's a tremendous sense of isolation for Wolverine") but with extended flashbacks.
Almost all the promotional materials for the film and the posters featured a shirtless Hugh Jackman; in contrast, he appears shirtless only in a handful of scenes in the actual film. This was done in order to emphasize the superior shape he got into for the film.
This is the second Marvel comic book movie for Will Yun Lee. He previously has played the villain Kirigi in "Elektra" (2005). The character Kirigi is also a ninja, since he does not appear in the traditional black suit in the movie.
Doug Walker aka The Nostalgia Critic had a cameo in the extra scene after the end credits and can be standing in the background behind Wolverwine. When Wolverwine turns around and sees that everybody at the airport has frozen in time.
The Fast and Furious and X-Men franchises have often released the same installments of a franchise in the same year. X2 and 2 Fast 2 Furious were both released in 2003, X-Men: The Last Stand and The Fast and the Furious: Tokyo Drift were both released in 2006, X-Men Origins: Wolverine and Fast and Furious were both released in 2009, X-Men: First Class and Fast Five were both released in 2011 and The Wolverine and Fast and Furious 6 were released in 2013. Furious 7 was set to be released in 2014, the same year as X-Men: Days of Future Past, however it then was pushed to 2015 after Paul Walker's death.
Logan refuses to use the name "Wolverine" until later on, when he finally declares it to his enemy Shingen before killing him. This is a homage to the storyline "Old Man Logan", where he renounced the title until the very end when his enemies had slain his family.
The Silver Samurai (Ichiro Yashida) in this film is a combination of Kenuchio Harada (a skilled mutant samurai with a tachyon blade) and his son Shin Harada (who possesses a technologically-advanced suit of armor). Harada himself is a separate character in the film.
When Wolverine is in the snowy forest, there is a bottle of whiskey called "Stanley's Whiskey" this is probably a reference to Marvel creator Stan Lee, who does not have his usual cameo appearance in this movie as the main characters were not directly created by him. Lee created Jean Grey who appears as Logan's conscience, and Professor X and Magneto who show up as cameos during the credits.