Director Ron Howard wasn't happy with Nicole Kidman's facial reaction during the shooting of the scene where her character lifts the bowl covering Joseph's (her husband Tom Cruise's) crotch. Without telling Kidman, he asked Cruise to remove his underwear. Howard got the reaction he wanted, and it appears in the film.
Although dialect coach Tim Monich had over 17 years of experience, this film was the first time that he had to teach his cast to speak in an Irish accent. Technically, Nicole Kidman's accent is incorrect. As a well-to-do landowner's daughter in Ireland at the time, she would have spoken with a largely English accent. That probably would have confused international audiences, so she was taught to speak in an educated Dublin accent.
Fungi the Dingle Dolphin, who receives a special thanks in the end credits, is not a captive or trained animal. He is a solitary common bottlenose dolphin that has lived in the Atlantic waters around the coast of Kerry, Ireland, since at least 1983. He frequently interacts with swimmers, boaters and kayakers, and has become a local celebrity and tourist attraction. As of 2017, he still appears in the waters.
The boxing scenes were filmed in the partially renovated train station in Billings, Montana. An abandoned Price Club in Billings served as both a factory to produce rubber chickens used in the movie, and a soundstage for the brothel. The brothel was built inside, and fire pumps were used to create rain.
Ron Howard asked Rod Steiger to audition for the role of Daniel Christie, which greatly infuriated the Oscar- winning actor. He did, but failed to win the part. Richard Harris was also asked, but he flatly refused.
Temple Bar, in Dublin's city center, was shut down for at least three months to accommodate the construction of the Molly Kay's bordello street set. Local shops and businesses were well compensated for the inconvenience. Despite that, the entire street set is only glimpsed briefly during the film.
The trivia item below may give away important plot points.
When the women are visiting the Christie's house, Shannon's mother tells her to play a nice piano piece. Shannon plays Beethoven's Moonlight Sonata. It's a reference to the code word "Moonlight" that Joseph is told when he is given the gun to assassinate Daniel Christie.