(CBS NEWS) – Fans who attended Lady Gaga’s Las Vegas show Saturday night were treated to a star-studded surprise when Bradley Cooper appeared onstage — and the pair sang the duet, “Shallow,” from their hit movie “A Star is Born.”

Cooper, who starred in and directed the 2018 film, was attending a performance of Lady Gaga’s “Enigma,” one of two shows in her Las Vegas residency at Park MGM resort, when she apparently called him out of the crowd.