Hilary Duff brought out Good Charlotte during her sold-out New York City show on Aug. 5, performing "The Anthem" with ex-boyfriend Joel Madden. The reunion came 20 years after the pair split. The show marked Duff's debut at Madison Square Garden, according to Billboard. Duff, known for the hit "So Yesterday," also revealed during the concert that her daughter had been in the emergency room that morning. She did not provide further details about the hospital visit. The crowd cheered as Madden and Good Charlotte joined her onstage, making the surprise collaboration a highlight of the night. Duff and Madden dated in the early 2000s, and their onstage reunion was the first time they had performed together since their breakup. The event was part of Duff's ongoing tour, and the sold-out crowd in New York witnessed a moment of musical nostalgia.