‘Saving Mr. Banks’ Trailer Reveals the Unknown ‘Mary Poppins’ Backstory

The new trailer for "Saving Mr. Banks" isn't just about seeing Tom Hanks as the legendary Walt Disney. It's about the true story of "Mary Poppins."

Or, rather, the true story behind the story of "Mary Poppins" that's really about saving author P.L. Travers's real life father.

Confused? Well, so was Disney when he tried to acquire the rights to Travers's book in order to make what eventually became the Julie Andrews-starring film and the author (played by Emma Thompson) wanted nothing to do with it.

As the trailer tells it, Mr. Disney – "You've gotta call me Walt" – promised his two children 20 years prior that he would bring Mary – "Poppins. Never ever just Mary!" – to the big screen and he's willing to do just about anything to make that happens.

First, he flies her out to Los Angeles for a meeting. She thinks it stinks.

Then, he offers her a glimpse at some of the supercalifragilisticexpialidociousness he has cooking in terms of songs and set designs.

Again, she's unimpressed.

Finally, he offers to escort her to Disneyland personally. Begrudgingly, Mrs. Travers bites. As they stroll down Main Street in a scene filmed at the real Disneyland, she reveals that Mary Poppins doesn't exist to save the children, she exists to save the father … her real father.

At the conclusion of the trailer – and their conversation – Walt has convinced the prim Mrs. Travers to ride on a carousel and make a movie.

Watch the full trailer for "Saving Mr. Banks" below: