Lady Gaga fans were treated to the first ever live performance of 'Shallow' at her Enigma show in Las Vegas on Saturday night (local time).
The pop icon was join by her A Star Is Born director and co-star Bradley Cooper to perform the hit.
"So a really good friend of mine... I don't know if you know him, but his name is Bradley," Gaga began telling the packed audience.
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"He made that movie, um, A Star Is Born. Yo Bradley, you wanna come up and do this one?"
The duet was a complete surprise to the crowd, who screamed with excitement when they worked out what was going on. The actor quickly joined her onstage, before throwing his cap into the crowd.
The pair looked right at home on stage in their first time singing together publicly outside of the movie, looking at each other warmly throughout the entire song.
Cooper and Gaga are expected to perform the duet at the Academy Awards on February 25 (NZ time).