PARIS — Taylor Swift sang "The Alchemy" as part of her acoustic set of surprise songs during Sunday's Eras Tour show with boyfriend Travis Kelce in attendance. Several football metaphors in the song have led fans to believe Swift wrote it about the Kansas City Chiefs tight end.

"Can you believe this is the 87th show?" Swift asked during her acoustic set in La Défense Arena. Kelce wears No. 87. She then played a mashup on guitar of "The Alchemy" from her new album "The Tortured Poets Department" with "Treacherous" from "Red."

Kelce stood in his box as Swift glanced up at him and the crowd looked back and forth between the two.

"This happens once every few lifetimes," Swift sang. "These chemicals hit me like white wine.”

The crowd roared.

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Kelce joined 40,000-plus fans for the fourth and final night of Taylor Swift's Eras Tour in Paris. He watched from a box seat alongside actor Bradley Cooper, super model Gigi Hadid and rock star Lenny Kravitz.

The concert marks the fifth time Kelce has appeared at the tour since the couple went public last year. His first stop was Buenos Aires, Argentina, followed by Sydney, Australia, and two nights in Singapore. Swift has changed the “Karma” lyrics to "guy on the Chiefs" every time Kelce has cheered her on from the sidelines.

Kelce hadn’t seen the new set list live since Swift switched up the eras and added her 11th era, “The Tortured Poets Department.” The singer-songwriter said she’s been working on the changes for 8-9 months (since last fall).

Hadid has famously been a member of Swift's squad for years now and has been dating Cooper for several months.

Other celebrities spotted in the crowd included Grey's Anatomy actor Jessica Capshaw and singer Christina Milian.

Her next stop is Stockholm, Sweden, as she continues the European leg of the tour.

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