During a recent appearance on Good Morning America, Jennifer Garner gave her thoughts on a 13 Going on 30 sequel. "What? Like, 15 Going on 50?” she said. “Let's simmer down, and then let's leave well enough alone." Though sequel culture is having a moment, Garner seems to understand one fundamental truth: Certain films are perfect as-is. 13 Going on 30, which celebrates its 15th anniversary on April 23, is one of them — and one of the best parts about it is the fashion.

The 2004 film tells the story of 13-year-old Jenna Rink (Christa B. Allen), who wishes herself into becoming 30 (Jennifer Garner) and goes on to reunite with her childhood best friend, Matt Flamhaff (Mark Ruffalo). As she comes into her own as both a 13-and-30-year-old, Jenna rights her wrongs in a way that’s heartwarming to even the most hardened rom-com haters, and she does it all while wearing an incredible time capsule of a wardrobe.

To glean more insight into the perfect outfits that Jenna wore as both an ‘80s teen and as a 2000s “30, flirty, and thriving” magazine editor, InStyle spoke with the film’s costume designer, Susie DeSanto. In addition to 13 Going on 30, DeSanto has designed costumes for other nostalgia-inducing rom-coms like Hope Floats, Miss Congeniality, and Little Black Book.Below, she weighs in on some of the 13 Going on 30's most iconic fashion moments.

The Babydoll Dress

Yes, that dress, the one Jenna feels herself up in during everyone's favorite dance scene. If the dress weren't enough, the whole look included Stila lip glaze, a giant blue butterfly pendant, Lucite studded bracelet, rhinestone cocktail rings, a hot pink baguette bag, chandelier earrings, spiky buns surrounded by assorted hair clips, and blue and pink strappy heels (which DeSanto said Jennifer danced in over and over again without losing energy).

“That’s actually a Versace dress we ordered,”DeSanto says. We never found it in the stores — it came from Italy. And [Jennifer Garner] had never even tried on the dress. We didn’t have any options and then… there it was.”

The Baguette Bag

When Jenna turns 30, she ends up wearing the perfect outfit for the type of glamorous identity crisis you have after you find a naked hockey player in your apartment. The full look is a pink slip with brown floral embroidery, a brown polka-dot coat with a notched collar, chunky open-toe silver sandals, and the crème de la crème of accessories: a silver sequin Fendi baguette bag, popularized in the early 2000s by Carrie Bradshaw and Sex and the City. (Earlier this year, Fendi revived the bag using Sex and the City as nostalgia).

“[The bag] was a thing that our director, Gary Winick, [picked out]," DeSanto says. "He grew up on the Upper West Side of New York, and his mom was quite the fashionista, so he really knew his handbags... I [also] met a guy who works for Fendi, told him what I was doing, and he was like, ‘You must use our purses. Pick whatever you want.’ We must have had 30 different Fendi bags. In the scene when she’s in her closet for the first time as a 30-year-old, those are all real [Fendi] handbags.”

The Godet Skirt

No matter how old you are, walking across the Brooklyn Bridge with a crush just isn’t the same if you’re not wearing a pink godet skirt and white tee that’s been embellished with a floral design and tied with a sweet pink ribbon.

“The further we got into Jenna getting closer to Matt, the more vulnerable and sweeter we made her,” DeSanto says. “There was one outfit, where they walk on the Brooklyn Bridge...she’s got that beautiful Chloé top, it was such a pretty neckline on Jen. It was a really romantic night and we were shooting outside in New York...It wasn’t that different from something [young Jenna] would have picked to wear to school.”

And don’t you dare forget your baguette bag, which is where you’ll store your bag of Razzles right before smooching the soon-to-be-married Mark Ruffalo with lips that have been tinted red by a candy that’s also a gum.

The Cardigan Set

Excuse us while we scour JC Penney for a rose-pink cardigan set that includes a tank with a nearly-invisible teeny-tiny heart. We wouldn’t dream of wearing this top without a deep, sleek side part. If you want to save your magazine from going extinct, wear this and this only.

Of colorful, nostalgic moments such as this one, DeSanto says, “It speaks to a time in fashion when things were more feminine and weren’t deconstructed yet...People were really wearing a lot of color. It was almost like fashion was doing the movie, because Moschino was doing some really fun stuff. We did lots of Miu Miu and Prada. They were all designing colors and fabrications that were for us, fitting into what we really needed.”

The Wedding Look

The wedding dress that Jenna wears in the movie is one of the her best looks, but it almost didn't happen. “That is an Angel Sanchez dress," DeSanto says. “What they had originally shot was a dress where there was a lot of tulle and they were bouncing on a trampoline. They were like, ‘Yeah, we could just use that dress.’ And then Jen [Garner] just looked at me and said, ‘I really think we could do better than that dress.’” With a quick turnaround, they found the perfect A-line dress, fingertip-length veil, and a pearl floral Cathy Waterman choker to go with it. “It spoke to this beautiful, optimistic, hopeful [bride]," DeSanto says.