ALTHOUGH HE'S done voice-over for animated films like "Monsters Inc." and "Cars," it's been 10 years since Billy Crystal has appeared as himself in a movie.

His "comeback" film is "Parental Guidance," opening Christmas Day, a sentimental comedy about two old-school grandparents (Crystal, Bette Midler) who spend a week parenting their new-school grandchildren.

Crystal loved the experience, he said, so we asked why he stayed away so long?

His answer: He was busy with his one-man show, "700 Sundays."

"I was busy creating that, and I did a year on Broadway, toured with it twice - I played Philadelphia with it - and did an Australian tour," Crystal said by phone from L.A. last Saturday. "Then I fell into the story of this piece, and it's taken me five years to get this movie made. Every time it looked like we were making it, something would happen.

"So, I was really just concentrating on and loving doing the play, and didn't care if I never did another movie. I was having too much, not just fun, but satisfaction, and then I didn't find anything I really liked. Then you turn around and it's been [10 years]. Wow.

"But it was worth the wait. I really love this movie."

In "Guidance," Crystal plays a minor-league play-by-play announcer who's sent to the showers before he's ready, and the movie is filled with the longtime Yankee fan's love of baseball, which he passes on to one of his movie grandsons.

Although a lot of his baseball chatter is improvised, Crystal said the bulk of his role is not ad-libbed.

"It's not ad-libbing," he said, "because I was in the room with [screenwriters Lisa Addario and Joe Syracuse] when we wrote. Once we knew where we were going, and Bette was on board, which I was thrilled about, I brought on Lowell Ganz and Babaloo Mandel, who'd written 'Parenthood,' 'City Slickers' and 'Splash.' They're also grandparents. So we had Lisa and Joey, who are credited with the screenplay, who are young parents, and they gave us all of that great stuff. And Ganz and Mandel put the polish to the things that Bette and I would say."

"This little movie has a lot of power," Crystal added. "It sneaks up on you because it's real - it's rooted in real things. We didn't set out to make a 'Cheaper by the Dozen,' we set out to make 'Grandparenthood.' The movie is about relationships and how important it is for grandparents to be in their kids' lives. The movie says don't let fractures happen so they end up being compound fractures. Heal yourself and heal your family, and know what's important in your life."

Reality and healing played a large role in the film's premiere, which was to take place two hours after our phone interview, one day after the Newtown elementary-school massacre. While there's no violence in "Guidance" and no children were spanked during the production of this film, there are scenes of children being brought to school.

"I'm going to introduce the movie," Crystal said of the premiere, "and I'm searching for what to say. I'm sure it'll be on people's minds and I hope that the overall feel of the movie, which is about family and staying close together, will resonate. I hope that it will help those of us who come in to the theater with a heavy heart."

Having worked in TV, movies and theater as a performer, writer, director and producer, Crystal said he has no favorite among the jobs.

"When I'm doing stand-up, I'm a comedian," he said. "When I'm producing something, I'm a producer. In this one, I wore a couple of hats: I created the story for it, I produced it and I'm in it."

And you're finally working with Bette Midler?

"We've known each a long time, and every time I bump into her at a party or at a dinner, I always come away going, 'She's great. I would love to spend more time with her.' "

So Crystal let Midler read the script, and they met soon after in a restaurant.

"We were married right from the beginning," he said. "She ate off my plate, she finished my sentences. It was really funny."