In striped ties, white button-ups, denim skirts and red blazers, the crowds outside Madison Square Garden last week looked more ready for a field trip than a pop concert. But on Thursday (a school night!) and Friday, fans basked in nostalgia and welcomed the return of RBD, a 2000s pop act born out of a telenovela.

RBD — a real-life group with real-life hits that just so happens to have evolved out of a fictional pop group — played two sold-out shows at the Garden to thousands of fans outfitted in early-2000s styles and renditions of prep school uniforms. Collegiate blazers and loosened neckties have been part of RBD’s signature look since the group debuted in the 2004 telenovela “Rebelde,” a Mexican remake of an Argentine series that followed a group of teenagers at the fictional Elite Way boarding school as they formed a band.

“As soon as I bought the tickets, I already knew what I was going to wear,” Diego Moreno, 32, a Venezuela native who lives in Chicago, said before the group’s Friday show. He wore a cherry red blazer bearing an Elite Way School patch, a white button-up, a red-and-white striped tie and a pair of Converse.

“There are different iterations of this school look,” he said. “Like, you’ll see some black jackets and black pants or even a blue button-up instead of white. But the red tie is what is usually consistent.”

Three hours before showtime, Taysha and Yava Aviles, sisters from Hazleton, Pa., waited in line outside the Garden on Eighth Avenue for the doors to open. For them, RBD represents their childhood and bond as sisters.

“It all started when we were in Puerto Rico in the 2000s,” Yava Aviles said. “We would watch the novelas on TV as sisters and wouldn’t miss an episode. Now we are here, and of course we came dressed.”

Taysha Aviles, 27, kept it traditional with a prep-school girl look and a small nod to Season 1 with a sky blue button-up. Yava Aviles, who is two years younger, channeled one of the stars, Dulce María, with red- and black-streaked braids and a Y2K cyberpunk outfit in matching red and black.

Among a sea of red ties and denim skirts, scattered cowgirls in pink showed there was more to the group than boarding-school chic. The looks alluded to the RBD ballad “Sálvame,” which figured in a 2005 episode in which Mía Colucci, played by the actress Anahí, sports a carnation pink cowgirl hat and matching snow jacket while shooting the song’s music video.

The look was the inspiration for Lisbeth Rojas of Brooklyn, who wore a silver and white take on Mía Colucci’s look. Ms. Rojas said that her shimmering eye shadow with a diamond silhouette had taken her an hour and a half to perfect, but that was nothing compared with the three hours she spent decorating her bejeweled cowgirl hat. “I barely finished it last night, but I’m so proud of it,” she said.

With so many references to RBD’s looks from fans, the group members themselves also celebrated their past onstage. Much of that came thanks to Kara Saun, creative consultant for the Soy Rebelde Tour.

Across the 27 cities and 54 dates of the tour, Ms. Saun is tasked with making sure members maintain their own style, but are also cohesive together.

“Each member has their own aesthetic,” Ms. Saun said backstage, as she held a green rhinestone boot. “Dulce is more glam rock, Anahí is girlie punk, Maite loves purples and fuchsias, Christopher likes more modern sleek, and Christian is amazingly out there.”

As RBD performed onstage, a team of artisans and tailors worked backstage, sewing garments, adding sequins and updating costumes. Each member of RBD has two traveling closets: one under the stage, where all the quick changes happen, and one backstage. To ensure everything runs smoothly, Ms. Saun has a team of four artisans from Los Angeles as well as local tailors at each night’s show.

“I love how the audience gets so excited at the end, when they come out in their iconic red school jackets,” Ms. Saun said. “On this tour we are referencing the past, but also updating the looks to who they are today.”

For the finale, five mannequins appeared onstage, outfitted with red coats. The group returned to the stage, illuminated by dim red lighting, and slowly put on their Elite Way jackets. Then, in unison, each member pulled a red tie from the front left pocket and let it hang unfastened.

Fans in their matching school uniforms and red ties — which were, of course, on sale at merch tables — screamed; others cried for this long-awaited school reunion.