Famous Titanic line Leonardo DiCaprio almost didn't say

Leonardo di Caprio and Kate Winslet in Titanic. Photo / Supplied

One of the most famous lines in Titanic almost didn't make it to our screens — all because Leonardo DiCaprio wasn't a fan.

The 1997 blockbuster's director James Cameron has opened up about having to convince the actor, who played Jack Dawson, to shout: "I'm the king of the world!" in one of the opening scenes.

In fact, it wasn't even the original line that was planned for the moment, in which Jack and his friend Fabrizio (played by Danny Nucci) are at the bow of the Titanic cruise liner.

"It was made up on the spot. I was in a crane basket, and we were losing the light. I had tried this and we had tried that, tried this line and that line and it was just coming up snake eyes," Cameron revealed in the BBC's Movies That Made Me.

"And I said, 'All right, I've got one for you. Just say, 'I'm the king of the world,' and just spread your arms out wide and just be in the moment and just love it and just celebrate it and love it.' And he goes, 'What?'"

The director explained he had to keep pushing the movie's star to do it.

"I'm getting this over the walkie talkie. 'I'm the king of the world,' just say, 'I'm the king of the world,' but you've got to sell it! And he goes, 'What?!' I said, 'Just f**king sell it.'"

Luckily, DiCaprio did — and it went on to became one of the most famous lines in cinematic history.

His co-star also recently opened up about the iconic scene, describing the brutal conditions the pair was forced to work in that day.

"Leo and I would go on a construction lift, and it would drop us off at the top, and then the lift would go away so that it wasn't seen during filming. We were trapped on this little tower with our set coats so that we wouldn't freeze," Nucci told Vanity Fair for its special 25 Most Influential Movie Scenes edition.

"We were up there for hours because you would have to bring the lift back in, take it up, and then have us go down. So, we were basically trapped up there. It was one of the most hysterical experiences. All I remember is we were very hungry. And at some point we both had to pee terribly and there's no like, 'Yeah, can we get the lift back in so that we can go to the rest room?' There was none of that."