Saving Mr. Banks” screenwriter Kelly Marcel was a “Mary Poppins” pro as a kid compared to the pic’s co-star Colin Farrell. “It was definitely the film we watched every Christmas,” said Marcel at a Q&A following a screening of Disney’s “Saving Mr. Banks” Wednesday at the ArcLight as part of the Variety Screening Series.

Farrell had a different childhood movie in mind.

“I’m sure I’d been shown (‘Mary Poppins’) one Christmas when I was way into single digits,” said Farrell. But “I was more of a ‘Willy Wonka and the Chocolate Factory’ boy. I was more interested in fizzy lifting drinks and Everlasting Gobstoppers than I was in spoonfuls of sugar.” But his involvement in the tale of “Poppins” author P.L. Travers and her run-ins with Walt Disney juxtaposed with a look at her childhood brought him closer to the “Poppins” musical. “I do feel an affinity for it now,” Farrell said.

Farrell finally got a chance to watch “Mary Poppins” during a pre-filming gathering at his house. “We all watched it together,” he said. “There were actors in the film that I knew I wasn’t going to get a chance to work with or meet … so I said to John Lee (Hancock, the film’s director), ‘Can we have everyone around to the house? We can put the film on and all sit around and cuddle,’ which we did, save the cuddling.”

After that, Farrell became a “Poppins” convert. “The film’s beautiful … I do feel an affinity for it now.”

According to Marcel, putting the film together was about as magical as Mary Poppins herself. She’d written the first draft not thinking that the film could only really be made by the Disney studio, but it was embraced by Disney right away, which opened up a wealth of research to her, including tapes of Travers’ conversations with Walt and other Disney denizens. And the magic carried over into the casting.

“John wanted to know literally everything that was inside my brain … so when it came to casting he asked me who I had in my head. Of course the people I had in my head were the real people,.” Marcel recalled. “When it came to casting P.L. and Walt, I had a list of two people and that was Tom Hanks and Emma Thompson. There wasn’t anybody else and this film was extraordinary because normally roles to out to actors and they say no, so you move on and we got the first person on the list for every single character.”