By now, you’ve very possibly heard the news, whether you wanted to or not: On Sunday, the 12-time Grammy Award-winning pop star Taylor Swift stoked recent dating rumors when she showed up at the Kansas City Chiefs game against the Chicago Bears to watch Chiefs tight end Travis Kelce lead the team to victory.

Ms. Swift ate chicken fingers and took in the game from a private box with Mr. Kelce’s mother, Donna. When the singer left the stadium after the game, decked out in Chiefs gear, Mr. Kelce, striding alongside her, wore a light blue and white denim jacket and pants set from KidSuper.

The image of Mr. Kelce and Ms. Swift together quickly went viral and sparked immediate interest in Mr. Kelce’s outfit.

The American designer Colm Dillane started releasing clothes under the label KidSuper in 2010. Mr. Dillane, 31, who has been lauded as the next Virgil Abloh, won the Karl Lagerfeld special prize from LVMH in 2021. In January, he collaborated with Louis Vuitton for its critically acclaimed men’s wear show. But on Sunday night, Mr. Dillane and his KidSuper co-workers were texting in their group chat about the unexpected surprise of Mr. Kelce’s outfit during such a high-profile paparazzi moment.

Mr. Kelce had worn the brand before, most notably on his way to the 2023 Super Bowl. (The Chiefs won.) But this was even more of an opportunity for Mr. Dillane and his team, the designer said: They knew instinctively that just being in proximity to Taylor Swift, whose popularity and influence is astronomical, could mean big things for the brand.

In the group chat, Mr. Dillane’s friend Doug Gleicher suggested adding a Taylor Swift reference to the official product names on the KidSuper website. Because the brand manages its website in-house, he said, it took KidSuper’s web developer, Adham Foda, “about one second” to change the “Bedroom Painting” denim set to the “1989 Bedroom Painting” denim set.

“All we did was write ‘1989,’” Mr. Dillane said. “We were like, ‘Ha-ha, this is funny,’ and then I tweeted it. Swifties of Cincinnati picked it up, and then it just went so stupidly viral.”

Many news outlets initially reported that Mr. Kelce specifically chose to wear an outfit with “1989” in the name as a show of support for Ms. Swift — the year is a reference to Ms. Swift’s blockbuster 2014 album, which featured hits like “Blank Space” and “Shake It Off” — though Mr. Dillane clarified on X that the brand had changed the name only after seeing Mr. Kelce wearing it. Still, the move to rebrand the set was immediately praised as part of a “genius” business strategy.

“Of course I’ve tried my absolute hardest in so many creative ventures and this is the one that took off,” Mr. Dillane said.

The 1989 Bedroom Jacket is now entirely sold out, and the pants are available only in small and medium. Mr. Dillane said that until Sunday, he wasn’t planning on restocking the set, “but now it’s like, maybe we’ll only make that item for the rest of time.”

Mr. Dillane said that while the virality of the 1989 Bedroom set did not financially change his life overnight, his friend’s parents who are “very Americana” were impressed.

Ms. Swift’s brief appearance at Mr. Kelce’s game has had such an effect on American popular culture that, in addition to boosting sales for brands like KidSuper, it also almost immediately spawned its own merch. One Etsy shop is selling an Eras Tour-themed Travis Kelce sweatshirt, while another is hawking a Chiefs-themed “Loving Him Was Red” T-shirt, an allusion to lyrics from the title track of Ms. Swift’s 2012 album, “Red.”

But the couple’s public debut also had a profound effect on Mr. Dillane, who says he is now an avowed Swift fan.

“I am a Swiftie,” Mr. Dillane said. “Now I’m going to go to every tour. I’m going to buy her merch. I think she made more money off of me than I made off of her because of how much I’m going to invest in Taylor Swift for the rest of my life.”