A Hollywood actor took the mic at a New York City comedy stage unannounced and launched into his full stand-up set under a fake name, The U.S. Sun can reveal.

The star has been frequenting the iconic Comedy Cellar, and he has brought a fellow A-lister with him to the sets.

Masked employee waiting outside The Comedy Cellar in NYC.

The Comedy Cellar is an iconic setting where many big-name comics got their startCredit: Getty
Will Arnett in Tribeca.

Will Arnett has been going to the Comedy Cellar in recent days, but oddly has been performing under a fake nameCredit: Getty

The actor in question is an unmistakable Will Arnett, 54, who has been confounding the comedy club’s audience by performing under an alias. 

“He goes up to do stand-up but has been using a fake name, and everyone in the audience is like, ‘But that’s Will Arnett!’ It’s really bizarre,” the source said.

Making Will’s recent appearances even more peculiar, he always brings Bradley Cooper, 50, along with him.

ROLE PREP

But a separate insider claimed Will is just performing on stage to prepare for his role in the upcoming film Is This Thing On?

The film is being directed by Bradley.

According to IMDB, the movie is about a man “exploring stand-up comedy in NYC” while his marriage falls apart.

Laura Dern and Andra Day will also star in the flick.

The Comedy Cellar recently hosted another very famous stand-up newbie, Madonna.

As The U.S. Sun reported, the Material Girl was spotted testing out new material after her friend Amy Schumer brought her up to the stage.

‘CHANGED MY ENTIRE LIFE’

Will and Bradley have a deep-rooted history together and were even once neighbors.

Last year, Bradley told People that Will helped him get sober.

The Hangover star said he remembered asking Will about a dinner that they had both recently attended. 

Will asked Bradley: “How’d you think that went?” 

“I was like, ‘Oh, I thought it was great,” Bradley recalled.

“And Will tells me, ‘You were a real a**hole, man, you were a real a**hole.”

Bradley called it “the first time I ever realized I had a problem with drugs and alcohol.”

“And it was Will saying that to me. I’ll just never forget it. I was like, ‘Oh, the guy that I think is doing mean humor is telling me the truth about that.’ And it changed my entire life.”

Bradley Cooper and Will Arnett at the "Goodnight, Oscar" after-party.

Will has been bringing his old pal Bradley Cooper along for his very random, and poorly disguised, standup setsCredit: Getty
Laura Dern at the SNL 50th Anniversary Special.

The pals are gearing up for a new film, Is This Thing On?, also starring Laura DernCredit: Getty
Madonna performing stand-up at the Comedy Cellar.

As The U.S. Sun previously exclusively revealed, Madonna took the stage at the iconic Comedy Cellar just last monthCredit: The U.S. Sun
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