On Saturday (Jan 26), Bradley Cooper surprised fans by joining Lady Gaga on stage at the Park MGM theater where the singer performs her Las Vegas residency ENIGMA for a performance of their duet "Shallow."

Since A Star is Born's Oct. 5, 2018, United States premiere, "Shallow" has taken on a life of its own. Although Gaga is known for her mega-hits, the track that is featured in the film is now her longest-leading track on Billboard's digital song sale charts. This coincides the success of the movie, which has grossed over $410 million at the box office.

A Star is Born has also been nominated for multiple Academy Awards, including Best Actor and Best Actress for the co-leads and Best Original Song for "Shallow."

Bradley Cooper isn't the only time Gaga has made headlines during her Las Vegas residency. On Jan. 21, the "Born This Way" singer attacked Karen Pence for teaching at a school that openly discriminates against LGBTQ students, calling Vice President Mike Pence and his wife the "worst" examples of Christianity