In the new movie "Are You There God? It's Me, Margaret," Rachel McAdams got to revisit her adolescence, but Abby Ryder Fortson is still in the middle of hers. The worst part of being a teenager for the 15-year-old actor? "All the awkwardness, obviously," she tells POPSUGAR. "There's days where I'm like, 'Wow, I just did something real stupid. And I'm like, 'Hmm, OK, we gotta work on that."

McAdams says that if there is something she misses about being a teenager, it's "that feeling of floating through day like a butterfly." She realizes now that as a teen she had a "lack of responsibility," adding, "I thought I had a lot going on, but really I didn't." Still, McAdams admits, "I don't truly miss a ton about being a teenager, to be honest. I'm sorry, Abby." Fortson agrees: "It's a hard time."

In "Are You There God? It's Me, Margaret" - based on Judy Blume's seminal 1970 young adult classic - Fortson stars as the titular Margaret, a middle schooler on the brink of puberty whose life is thrown into chaos when her parents move their family to the suburbs. The film traces Margaret's journey through a school year as she deals with friends, puberty, religion, and her first crush. McAdams stars as Margaret's mother Barbara, whose role was expanded for the movie.

Fortson hadn't read the book until she got the audition for the film, but she felt the story's impact immediately. "I turned to my parents and I said, 'Oh my God, how did someone write down exactly this experience? How did someone write down exactly how this feels?'" she remembers. "It's such an incredible feat that Judy was able to, like, create a story that is so relatable to so many people, and I absolutely loved it, and it made me fall in love with the project."

McAdams also hadn't read the book until the film came around and she said it was interesting to read it as a mother now, looking for the mom's point of view. But she didn't just identify with the parental part in the story. "What was so interesting was that I still related to Margaret," McAdams explains. "I got all kinds of great juicy tidbits and stuff about my character, but it was like, 'Oh yes, that's why this is so timeless. This is taking me right back, and I'm having all the feels about that time of my life.' And it's really stuck with me."

Margaret has to deal with the joy and pain of her first crush in the book and movie, and Fortson and McAdams have both been there, too. "It's always awkward," Fortson says. McAdams adds that she "probably" had her first crush in nursery school. "He never wanted to play house, he thought it was boring," she says. "I remember . . . stealing a kiss on the back of his neck once, and he was so upset."

As for celebrities who caught her eye in her youth? "I remember seeing Conan the Barbarian and having a little funny feeling in my tummy," McAdams says of the first celeb crush she remembers. She checks with Fortson that the teen knows Conan was Arnold Schwarzenegger, and she does. Watch more of their interview with POPSUGAR above.

"Are You There God? It's Me Margaret?" is in theaters now.