Jason Schwartzman has formed an unlikely musical alliance with the songwriter he portrays in new movie Saving Mr. Banks.

The actor plays Disney composer Richard Sherman in the film and the odd couple has been performing together to help promote the new movie, which chronicles Walt Disney's efforts to win the film rights to P.L. Travers' beloved book Mary Poppins.

Schwartzman says, "We're been going around... I've had to do a lot of things that are quite frightening for this movie and singing publicly... is quite scary."

He also found himself performing songs from the movie for co-star Emma Thompson and Sean Penn.

Schwartzman adds, "We did a performance at the Beverly Hills Hotel for Academy members and Emma Thompson... comes in with a bunch of her friends, and one of them is Sean Penn, who is a bada** and the epitome of macho powers.

"I go up there and we're singing, like, Chim Chim Cher-ee... and we're having fun... and it dawned on me that I was trying to act tough while singing these songs in front of Sean Penn.

"Later, I did see him singing along. He was into it, but he looked so strong doing it... He looked amazing. I was too afraid to meet him afterwards."