MGK‘s show in Rosemont, Illinois, on Thursday night was part concert, part friendship love fest, with Halsey surprising the crowd by joining her longtime pal on stage for an electric performance of “Bad Things.”

At one of the final 2025 dates of the rapper-turned-rocker’s Lost Americana tour, the pop star came out for an unexpected duet on MGK’s nine-year-old Billboard Hot 100 hit “Bad Things.” “Am I out of my head? Am I out of my mind?/ If you only knew the bad things I like,” Halsey sang, taking over Camila Cabello’s part on the song. “Don’t think that I can explain it/ What can I say? It’s complicated.”

While she was onstage with him, MGK gave a sweet speech honoring how his friend has overcome numerous health struggles in recent years, including lupus and a rare T-cell lymphoproliferative disorder. “I wanna give flowers to this amazing woman, who’s had a very, very, very tough couple of years,” he said as Halsey blushed. “Health scares that I got to personally watch her fight through, and I don’t know if we’ve acknowledged that enough, how much you mean to music, and how much you mean to me as a friend.”

“Seeing you that way during the time, and seeing you now …,” MGK added in clips captured by fans at the show. “I mean, this girl is still going through chemotherapy and fighting every day, and she’s out here crushing it.”

Halsey has been open about facing difficult health challenges, revealing in 2024 that they’d been diagnosed with lupus and T-cell disorder two years prior. Before embarking on her own Back to Badlands Tour in October, the singer underwent another round of chemotherapy.

MGK and Halsey have been friends for years, teaming up in 2020 on “Forget Me Too” for the former’s Tickets to My Downfall album. In 2022, Halsey appeared on stage with MGK at his Mainstream Sellout Tour show in Los Angeles.