The mother of three also dished on her first time moving to L.A., and getting back into 'Alias' shape.
Jennifer Garner may be an A-lister, but she still gets starstruck.
ET's Cameron Mathison sat down with the 45-year-old actress and her The Tribes of Palos Verdes co-star, Maika Monroe, at the film's junket on Friday, where Garner revealed who she still gets giddy seeing out and about.
"I am starstruck by children's book authors, big time," she revealed. "I met Marla Frazee and was just, didn't even know what to say to her. I am starstruck by ballerinas, big time. I am starstruck...I heard this woman play the saxophone the other day, she was so amazing. I couldn't look at her after. Just anyone who can do something that you can't do."
"Barefoot Contessa!" she added.
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While Garner gushed about her idols, Monroe, 24, couldn't stop singing Garner's praises. The two play mother and daughter in the film, which centers on their family's move to the idyllic and affluent suburb of Palos Verdes in Los Angeles -- and the drama that ensues.
"This comes from the bottom of my heart. I don't think I've met a more genuine, more talented, literally, it was a hard movie for both of us. It was just, every day was a different thing, and what Jen brought to set, I have so much respect," she raved. "I wanna grow up to be you."
"Oh my gosh," Garner replied, agreeing that their emotional roles (Garner's character finds out her husband is cheating on her) definitely took a toll.
"The character is something so different from anything I've played before. I usually play characters who are more kind of buttoned-up than I am in real life. To play somebody who is this just coming apart at the seams was exciting, terrifying but exciting," she said. "I went home to kids and a busy house, so I didn't really have a choice [of whether or not to shake it off]."
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The mother of three also dished on her first time moving to Los Angeles, admitting that she found similarities between herself and her character's tough adjustment at first.
"I did have a hard time leaving. I lived in New York first, and I moved out here and felt like, 'What did I do?'" she confessed. "I really had to make the decision to be happy and figure out what the things are that I love about it here, and do them constantly. They were hiking, farmers markets, cooking, yoga... I found a few things and the work followed."
Now, Garner's career couldn't be hotter, as the actress is about to start working on an action film, Peppermint -- and has showcased her intense training on Instagram.
"[It's] super fun. It's my same stunt double [from Alias]," she revealed. "She's like a sister. It's so great. She's the best."
"I been doing tutu Tuesdays to celebrate different ballerinas, because I love them so much and I stalk them on Instagram. And I just one night was on Amazon and clicked. And then stunt people are so game for anything that when I said to these big men, put tutus on, they didn't even bat an eye, they just put them on," she explained of her Instagram video. "We just did the whole two-hour rehearsal with them on, nobody even questioned."
Garner also opened up about the importance of supporting women in the industry.
"Just keep seeking out women because we don't get to work together very much and you have to insist on having women as part of your job life, your career -- not just outside of work, but work. And if you find one, hold onto them," she shared.
"It's your responsibility to call me if you need something, and it's mine to say, 'Come on up, what can I do? How can I help you?'" Garner continued, addressing Monroe. "Look after the other women around you and make sure you are going around them if you need them."
The Tribes of Palos Verdes hits theaters on Dec. 1.
See more on Garner in the video below.