Both Hargitay, 51, and Delevingne, 22, were featured in the star-studded and action-packed music video for Swift’s single “Bad Blood.”
“Couldn’t even contain my happiness because @caradelevingne and @therealmariskahargitay surprised the crowd tonight,” Swift captioned an Instagram photo of the three posing onstage during the show.
The stars danced and sang alongside Swift while she performed her hit single “Style.”
“Justice and Mother Chucker at #1989TourPhilly,” said of another photo of the trio, referencing the women’s “Bad Blood” alter-egos.
Hargitay, who’s Law and Order: SVU character is Swift’s cat Olivia’s namesake, and Delevingne wore all black ensembles, while Swift stunned in a sequined silver fringe number.
Pop band Echosmith also joined the songstress on stage Friday for a rendition of their hit single “Cool Kids.”
Hargitay and Delevigne aren’t the first “Bad Blood” alums to join the tour. Swift brought out models Martha Hunt and Gigi Hadid during a 1989 May stop in Detroit. The blond beauties also strutted the stage with the singer during “Style.”