Las Vegas, Jan 27 (IANS): Actor-director Bradley Cooper made a surprise appearance at Lady Gagas show here.

The crowd at Las Vegas' Park Theater was treated to Cooper's surprise appearance during Gaga's finale performance of the song "Shallow", according to hollywoodreporter.com.

The song, which was nominated for an Academy Award earlier this week, is the closing number of the "Enigma" show, the residency that kicked off in December last year.

Attendees had no idea a duet was in store when the actor appeared on stage. The two embraced and he followed Gaga to the piano.

"I even got you in ears," Gaga told Cooper of the monitors used during live stage performances.

"I can't hear anything," he cracked.

Following the performance, as each of Gaga's dancers took a bow and introduced themselves, Cooper shyly joined in and said: "Bradley, thank you." He then pitched his baseball cap into the crowd.

"Shallow" is slated to be performed at the Oscars in February, reported variety.com.