But Fonda and J-Lo both seem happy to show their sillier sides in this weekend's "Monster-in-Law," (search) an over-the-top send-up of frosty mother-in-law/daughter-in-law relations.
"I was ready to laugh — and I mean it just was so serendipitous that I had an opportunity to play this outrageous character," Fonda told FOX News.
"I'm very different today and ready to laugh, and this character came along that's bigger than life and over the top and I thought God, wouldn't that be fun to try and see if this new lighter person that I am could embody her and have a good time doing it? And I did," she added.
Fonda plays Viola Fields, a high-powered, veteran news anchor patterned after Barbara Walters who has a meltdown after she's fired for being too old. But she emerges from psychiatric treatment with the comforting thought that she still has her son Kevin (Michael Vartan (search)), who has become a hot young surgeon despite Viola's incessant smothering.
He has also managed to fall in love — with Lopez' character, Charlie Cantilini. But there's one minor problem: his mother, who hates Charlie and doesn't want to lose her son.
In the movie, we get to see the usually glamorous J-Lo being pounded face-first into a cake and otherwise humiliated.
"We saw a different side of me — I think this character was a little bit different for me — she's a little bit goofier I think than you've ever seen me," Lopez told FOX News.
The movie even allows Lopez a chance to poke fun at her famous posterior, when Viola gets a too-small couture gown for Charlie.
"It's a romantic comedy," Vartan told FOX News. "But one of the things I liked about it is there's more comedy than romance."
The movie is also getting attention because it's Fonda's comeback — it's been 15 years since the actress, who won Oscars for "Klute" and "Coming Home," was last on the big screen (in "Stanley & Iris").
"I quit 15 years ago because I was very unhappy and I was living on willpower, and you can't be creative when you're living on willpower. I just didn't want to be scared anymore so I quit," Fonda told FOX News.
It's also a bit of a return for Lopez, who's happy to give the press something to focus on other than her love life.
"When you're promoting your stuff and you can get out there and talk and let people know things are out there ... that's all part of the work when you do business and that's fine.
"But the other way I don't think it's important to be out there — I don't need to be on the cover of these magazines every week. That doesn't help in any way — in fact I think it hurts things. So I'm glad that I kind of pulled away from that," she said.
"I don't like people to see me when I'm going to put out my garbage."
FOX News' Mike Waco and William La Jeunesse and the Associated Press contributed to this report.