James Cameron's Titanic may have been three hours long, but Leonardo DiCaprio gave a spectacular performance as Jack Dawson, which dramatically altered the actor's life. Fan theories even spread about his Titanic character. Additionally, Kate Winslet shared captivating chemistry with DiCaprio as Rose DeWitt Bukater, but her role almost went to DiCaprio's Romeo + Juliet co-star Claire Danes.

While acclaimed actors were already featured in Titanic, the film almost went with a much bigger star -- Robert De Niro. De Niro and DiCaprio had previously collaborated on the 1993 film This Boy's Life and Marvin's Room the year before Titanic. Even without De Niro, Cameron's Titanic still grossed an absurd amount of money and struck gold at the Academy Awards. The film was even re-released in 3D for the 100th anniversary of the sinking of the Titanic in 2012.

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The 1997 film Titanic followed the epic love story between first-class passenger Rose DeWitt Bukater and third-class passenger Jack Dawson. Rose was engaged to 30-year-old Cal Hockley (Billy Zane) when she boarded the Titanic to solve her family's financial ruin after her father spent almost every cent before his death. However, Cal treated Rose poorly, and she found comfort in Jack. Rose and Jack began a relationship, much to her mother and Cal's objections. The new couple remained on the Titanic until the ship sank into the frigid waters of the Atlantic.

Rose managed to survive the freezing temperatures, but Jack met his unfortunate fate, as they could not find a way for both to fit on the floating door. Years later, Rose recounted their ill-fated love story in 1996 after Brock Lovett and his team surveyed the Titanic wreckage in search of the Heart of the Ocean necklace. While Rose and Jack were largely fictional characters, some actual historical figures found their way into Cameron's Titanic -- like Captain E.J. Smith and Bruce J. Ismay.

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Bernard Hill as Captain Smith in Titanic (1)

De Niro has starred in many genres but is largely known for his performances in gangster movies like Goodfellas. He was originally offered the part of Captain Smith before he was forced to turn down the role. De Niro had a nasty gastrointestinal infection at the time and was unable to fulfill his acting duty, per The Mirror.

Bernard Hill was recruited to replace De Niro, who was arguably the better decision for the part. This is partly because Hill actually bore an uncanny resemblance to the real-life Captain Smith. While it was a minor role, Smith's final scene struck a chord with viewers in how he went down with his ship.

A huge star like De Niro could have ultimately mesmerized viewers and distracted them from the character's important role in real-life and the film. Despite his inability to star in Titanic, De Niro still appeared in three films during the same year. Hill's performance as Captain Smith opened doors for his acting career. He later starred as King Théoden in The Lord of the Rings. Despite the countless actors who could have been in Titanic, the ultimate cast was rightfully chosen for the film.