Grease

Grease and cheese ... Newton-John and Travolta in the finale of their film.

Grease fans have waited three decades for Danny Zuko and Sandy Olsson to team up again, so there was plenty of anticipation surrounding the new music being recorded by the actors who portrayed them, Olivia Newton-John and John Travolta.

Who knew, 34 years on, the famous onscreen duo would end up working on a Christmas album?

''We don't like to rush things,'' Newton-John says with a laugh, chatting over the phone with Fairfax and her long-time friend, Travolta.

Olivia Newton-John and John Travolta now.

Olivia Newton-John and John Travolta now.

He says repeatedly plugging themselves as Danny and Sandy after the smash-hit 1978 movie was never their style.

''Olivia and I are not aggressive people in that way, meaning we don't push ourselves on people,'' Travolta says. ''Grease was so big, I'm not telling you anything you don't already know.

''[It is] the biggest musical in history plus the biggest pop duet in history. If you do anything trying to take advantage of that too much, people don't respond to it. But if you wait a long time, like we have, and it's really organic … it feels more acceptable to present ourselves in that way.''

The idea for a Christmas album, which also includes guest appearances from Barbra Streisand, Tony Bennett and James Taylor, came from Travolta while he and Newton-John were texting each other.

At first Travolta suggested a Christmas song, then a few weeks later, when the pair bumped into each other at an event, he proposed an album.

''I thought that was a wonderful idea, I wish I'd thought of it,'' Newton-John says. ''Then I said, 'How about we do it for our charities?' and that was the clincher.''

It was as much about their love for Christmas - and raising funds for charity - as it was a present to the Grease fans. ''[Grease has] given people such joy and it's a No. 1 movie, my most successful movie … That's the one I can guarantee [will have] the most positive effect on others,'' Travolta says.

Newton-John is still amazed by the success of the film. ''And who knew when we made this, that it would still be giving so much pleasure to people?''

She still has the famous skintight black trousers from the final scene, when the pair sang You're the One That I Want.

''They're in my closet … and the jacket.'' ''You still have yours?'' Travolta exclaims. ''You are so smart. I think mine went to donations earlier. I get to own wardrobe but I tend to just give it away.''

Both are happy to watch the movie again, with Newton-John saying she is now removed enough from it to watch without analysing her performance.

''It came on [television] on the tour bus recently,'' she says. ''I sat there with my band … and I really got to watch it without critiquing myself, because it's so long ago now, I've let go of that.

''There's never a dull moment in that movie, it just keeps moving. It's got such energy.''

Travolta said Newton-John contacted him afterwards.

''She texted me saying, 'Boy, you were cute!' She fell in love with me again, I liked that part of it,'' he says, with a laugh.

The video for their new track, I Think You Might Like It, is a far cry from their smooth moves at Rydell High. Some critics are describing it as the cheesiest Christmas video ever made. But it is for a good cause.

The charities benefiting are the Jett Travolta Foundation and the Olivia Newton-John Cancer and Wellness Centre in Melbourne.

Travolta and Newton-John's album This Christmas is out now through Universal Music and Grease Sing-a-Long screens at the Moonlight Cinema on December 27.