"Garry Marshall was the reason I think most of us said yes to this movie," she says of the cast that includes Julia Roberts, Kate Hudson and Jason Sudeikis. 

"Without even reading a script, it was a definite, 'Yes! Where do you want me and when?'" she says. "I mean, we were raised on Garry Marshall - Happy Days, Laverne & Shirley, The Odd Couple. And then his movies - Pretty Woman, Beaches. It's sort of one of your dreams as a young actor to be in a Garry Marshall movie."

Jason Sudeikis and Jennifer Aniston reunite once again in Mother's Day

And working with him lived up to her expectations. "It's as if Garry just walks with sunshine wherever he goes," Aniston laughs. "And it shows in his crew. He is beloved and adored, and I think a lot of people are here just to be able to be with him. The set is a full-on family affair."

She also enjoyed the way Marshall directs a film, allowing the actors to play with their characters. "Garry lets us improv," she says. "Sometimes we go on and on, and we should be cut sooner than we are! But that's the fun of it."

In the film, Aniston plays Sandy, a woman who discovers that her ex-husband Henry (Timothy Olyphant) has remarried "kind of out-of-the-blue and quickly", and now Sandy has to come to grips with the fact that Henry's much younger new wife (Pretty Little Liars' Shay Mitchell) will be involved in raising her children. "She has to overcome the challenge of sharing her children in a very short period of time, digesting all that information and sort of rising above it," Aniston says. "And she's just thrown by the fact that the new wife is a much, much younger woman. Of course, this is a complete game-changer, because it's a big deal when another person comes in as a co-parent to your child."

The film also reunites Aniston and Sudeikis for their fifth film together. "Well, now we should just continue off into the sunset at the rate we've been doing movies together," Aniston laughs. "It just makes it quite comfortable and fun and familiar in all the best ways. Can't stop, won't stop!"

Watch the trailer for Mothers Day: