Songs from favorite movie classics like "Chim Chim Cheree" from "Mary Poppins" and "I Wan'na Be like You" from "The Jungle Book" have a way of sticking around through the ages.

But has anyone ever stopped to wonder who wrote the iconic songs?

The answer is Richard Sherman, who with his late brother Robert, fulfilled Walt Disney's dream of bringing Mary Poppins to the silver screen.

"Bob and I were handed this book by Walt and he said, 'Read this and tell me what you think,' said Sherman. "We were actually thrilled and enchanted by the character…and terrified of the fact there was no plot whatsoever in the book."

TOM HANKS ON BECOMING WALT DISNEY

But the brothers went on to pen those Oscar-winning songs.

Now the movie "Saving Mr. Banks" is coming out centered around the production of "Mary Poppins," starring Tom Hanks as Walt Disney.

"Those chimney sweeps doin' that, "Mary Poppins, step in time," that, that got my heart racing as an 8-year-old kid when I saw it," said Hanks.

Richard is played by Jason Schwartzman in the movie and Emma Thompson is Mary Poppins' cantankerous creator, PL Travers.

Travers didn't like Americans, cartoons, movies, music or Walt Disney himself. She didn't like much.

Sherman said Thompson captured Travers spirit perfectly.

"This lady, she captured this woman," Sherman said. "It was like looking at home movies as if somebody had shot movies of my brother and myself going through this period."

PL Travers hated Supercalifragilisticexpialidocious, but the team went ahead with the song anyway and it's a staple in the movie.

And as for the iconic backwards part of the song: "Julie Andrews is the first person that ever, ever, ever said that because … it was her idea," Sherman told ABC News. "And I think it's just marvelous because it was an added thing to supercal."

The movie was a phenomenal success. The Sherman brothers won two Oscars and launched their careers. Fifty years later, Richard Sherman still lives and breathes a happy tune.

Tom Hanks portrays Walt Disney in a scene from the film "Saving Mr. Banks." François Duhamel/Disney

The Walt Disney Co. owns ABC News, this website, and Walt Disney Pictures. "Saving Mr. Banks" opens Dec. 20.