Nearly 15 years ago, 13 Going on 30—a body-swapping rom-com in the vein of Big—arrived in theaters and charmed audiences everywhere. The movie revolves around Jenna Rink, a geeky teen who goes to sleep on her 13th birthday in 1987 wishing to be “thirty and flirty and thriving,” and wakes up the next day in her Manhattan apartment all grown up.

Jennifer Garner, in her first lead movie role, played the adult Jenna, who works for troubled fashion magazine Poise. She spends most of the film trying to reconnect with childhood friend/love interest Matt (Mark Ruffalo) and coming to terms with adulthood. Though the film came out the weekend before Mean Girls, it went on to gross $96 million worldwide (which was less than the $129 million Mean Girls earned, but still not too shabby). To celebrate the beloved film's 15th anniversary, here are some things you might not have known about 13 Going on 30.

1. The studio was worried that director gary winick would turn it into an "art film."

Director Gary Winick made a name for himself with the 2000 film Tadpole, and became a pioneer of the indie film scene, advocating for digital technology and how it could turn storytellers into bona fide filmmakers. Though his previous work was nothing like 13 Going on 30, Winick told the BBC that it was because of Tadpole that Garner requested to work with him on the project.

"Me and Jennifer said, ‘It’s got to be about something,'" Winick explained. “The studio was concerned that I’d turn it into an art film, and I was like, ‘You can’t turn this into an art film! But I can hopefully elevate it and make it better than it is.'"

2. Jennifer Garner hung out with 13-year-olds to prepare for the role.

The film’s production notes mention how Garner spent time with adolescent girls—including a 12-year-old friend—to get into the teenage mindset. “A kid of 13 can seem like an adult, but that can be deceptive,” she said. “You always have to remember they are also incredibly vulnerable, skittish, and childlike. Finding that balance was challenging.”

3. The “Thriller” dance became a major sticking point.

One of the film's most memorable scenes involves Garner and Ruffalo's characters awkwardly recreating the zombie dance from Michael Jackson's "Thriller" video—a scene that Winick didn't quite understand. In an interview with The Telegraph, Winick explained that the studio was adamant that he stage the dance scene. “I kept saying ‘What does that have to with the story?’ and they kept saying ‘We need to put it in the trailers.’ I had to force them to make it work as part of the narrative.”

Ultimately, the dance isn’t in the movie just to be there: Jenna gets her co-workers and friends to dance as a way to save a magazine launch party. “I didn’t want it to feel like a music video,” Winick said in the production notes. “I wanted it to work dramatically. As good as the dancing is, the reason the scene works is because it’s plot-oriented. Jenna is saving the party the way a 13-year-old would, not an adult.”

4. Mark Ruffalo almost turned the part down because of that dance sequence.

In an interview with Blackfilm, Ruffalo admitted that the embarrassment you see on his face in that "Thriller" scene is 100 percent genuine—so much so that he almost turned the movie down because of that single scene.  "The dancing was horrible," he said. "I almost didn't want to do this movie. I literally read it and I'm like 'I can't do this movie. I can't get up and do those scenes.' ... When [Jennifer] dragged me out [onto the dance floor in the film] she was literally dragging me out. I had hours of rehearsal with a dance coach who taught me how to do all the moves and stuff and still, when we got into actually shooting it and there were 300 extras around, I did not want to do that scene."

5. It featured some soon-to-be stars (including one Oscar winner).

In the flashback scenes to Jenna as a teen, you might notice a couple of familiar faces playing members of the popular clique known as Six Chicks: Pretty Little Liars star Ashley Benson and future Oscar-winner/current Captain Marvel Brie Larson.

6. Judy Greer doesn't think her character was a villain.

Judy Greer plays Lucy, who Jenna knows both as a kid and works with as an adult. Though Lucy manipulates Jenna a lot, both as a teenager and as a thirtysomething, Greer didn't see her as a villain. "I never consider a character I play a villain, even if they are a villain, ‘cause real villains don’t think, ‘I’m a villain,'" Greer told Today. "They just think what they’re doing is right.” (Though she did say it was fun to play “mean.”)

7. Greer didn’t think the younger version of her looked liked her. But everyone else did.

Alexandra Kyle played the 13-year-old version of Greer's character, Lucy. When Kyle met Greer’s mom, she said “It’s like seeing my daughter again,” Kyle said in the behind-the-scenes featurette.

“Gary and the producers all thought she looked so much like me, but I think she’s so cute,” Greer said. “They’re like, ‘Did you look just like her when you were her age?’ I was like, no, I looked like a little boy, and she’s gorgeous.”

8. Andy Serkis had to work hard to find his character's balance.

In the behind-the-scenes featurette, Andy Serkis—who played Richard, Poise’s editor-in-chief—said he had to work to find “that balance between [Richard's] flamboyant nature and actually keeping the reality of who he is and the stress he’s under.” Serkis said Winick probably got frustrated with him, though.

“He [kept] coming up to me and going, ‘Bring it down, just bring it down,'" Serkis explained of his director's instructions. “I kind of think I’m doing nothing here and he’s going, ‘bring it down.’ I’m thinking, if I bring it down anymore I’m going to be lying down. Having done Golem for ages, my face has gotten more animated. I make Jim Carrey looked relaxed.”

9. Garner and Winick “had the most successful collaboration possible.”

Carlo Allegri, Getty Images

In 2011, Winick passed away from brain cancer. In an interview with Entertainment Weekly following the director's passing, Garner shared just how much she loved working with Winick on 13 Going on 30. “Gary and I had the most successful collaboration possible," she said. "I don’t mean success in terms of box office, or from anyone else’s point of view other than my own. I left it better at what I do.” She also revealed that they planned on working on more projects together, but “didn’t get them done quickly enough.”

10. Jenna had a very expensive lifestyle.

Entertainment Weekly broke down just how much it would cost real-life Jenna and Matt to live in Manhattan, and it turned out to be a pretty tidy sum: Jenna’s Fifth Avenue apartment would cost $5 million, or $10,000 per month to rent. A pair of Manolo Blahnik shoes, of which Jenna has several, cost around $995, and just one Gucci purse goes for $1800. Matt, meanwhile, lives in the West Village. And even though he’s portraying a struggling photographer, he manages to cough up $5000 a month in rent.

11. Ariana Grande watched (and maybe still watches) the film every night.

In November 2018, Grande released the music video for her hit song “thank u, next.” It pays tribute to Mean Girls, Legally Blonde, 13 Going on 30, and Bring It On. In one part of the video, a disheartened Grande—like Jenna Rink—carries the dollhouse Matt built for her. Garner saw the video and complimented the singer on Instagram. “I watched this movie every night before bed growing up (and I still do sometimes, especially when I’m sad),” Grande replied. “And by sometimes, I literally mean every night still.”

Hannah Lux Davis, the video’s director, told Pitchfork that the dollhouse scene was originally going to be in the beginning of the video. “I cut together scenes from the original films to see how the pacing would look,” she said. “[The 13 Going on 30 scene] just wasn’t feeling natural there, but then you get to that third verse when Ariana talks about the wedding and walking down the aisle with her mom. It had a more organic structure that way.”

12. The film is about second chances.

“I chose 13 Going on 30 because it had more substance,” Winick said in the film’s production notes. “It’s about second chances. It’s about getting everything you ever wanted only to realize that none of those things make you happy, and then having a second chance to make the right choices.”

13. Christa B. Allen still gets recognized as Jenna Rink.

Carlo Allegri, Getty Images

Christa B. Allen was just 13 years old when she was hired to play the younger version of Jennifer Garner's character in 13 Going on 30. It was her first credited role, and she had a lot riding on her shoulders. Though she's now 27 years old, she recently told Today that she still gets recognized for the film. 

“I think because it meant so much to so many people, and it was just such a beloved film, that people are all so excited to see a person that was part of that zeitgeisty moment in the flesh,” Allen said. She also confirmed that she's looking forward to turning the big 3-0 herself. “People always quote back ‘30 and flirty, and thriving,'" Allen said. "I can't wait for that to be the theme of my 30th birthday."