Olivia Newton-John, 64, and John Travolta, 58, celebrate the season with cocoa and their new album, "This Christmas." — Courtesy Universal Music Group

For the first time in three decades, Grease costars Olivia Newton-John and John Travolta have reunited on record with a new holiday album, This Christmas.

AARP caught up with the old friends, who talked about switching roles on "Baby, It's Cold Outside" (Travolta sings the reluctant girl's part), their favorite holiday songs, and how their personal heartbreaks inspired them to step into a recording studio together one more time.

AARP: It's just a charming Christmas album.

(Unison) Thank you!

AARP: Whose idea was it to reverse the roles on "Baby, It's Cold Outside"?

Travolta: (To Newton-John) Was it yours?

Newton-John: It was us!

Travolta: Well, it wasn't my idea. It was Olivia. I agreed. (Laughter)

Newton-John: We thought it would be a little cheekier.

Travolta: I have an actor's viewpoint, so I said, 'I'll do it if I can play it like, "I don't want to go, Liv, but I know it will be just too naughty if I stay ..." '

Newton-John: (Laughs)

Travolta: Like, "Oh my God, if I stay we're gonna do such bad things …"

Newton-John: (Hysterical laughter)

Travolta: "Oh, Liv, I really gotta go!"

AARP: That's a very complex reading of that song.

Newton-John: (Still laughing) We really had a good giggle!

AARP: You know those radio stations that start playing holiday music around Halloween? Which of these tracks would you like to hear playing on one of those stations 20 years from now?

Travolta: Oh, boy, you know, the best thing about this album is nobody can decide what their favorite cut is.

Newton-John: What would you pick, Bill?

Travolta: There you go!

AARP: Well, that's not fair.

Newton-John: Oh, yeah it is! (Laughs)

AARP: OK. I love your version of "The Christmas Song."

Newton-John and Travolta: (Unison) Yeah!

Travolta: Yeah, me, too. You know what? That is one that I would pick! (Laughs)

AARP: I like how it starts with the deceptive piano vamp; you think it's gonna be …

Travolta: "One for My Baby and One [More] for the Road" [the classic Frank Sinatra barroom ballad]. But then it becomes "The Christmas Song."

Newton-John: Yeah, it was John's idea to do that like a bar song.

Travolta: "Have Yourself a Merry Little Christmas" is very touching.

AARP: That was written as a sad song …

Travolta: Yes!

AARP: … And it's not often that singers bring out the melancholy in it, but I think you guys did.

Travolta: Yeah, thank you. I do, too.

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