King Princess Covers The Strokes' 'You Only Live Once' with Julian Casablancas in NYC — Watch!

King Princess brought out a fellow New York City native rock star for her show at Radio City Music Hall.

During the 23-year-old "Let Us Die" singer-songwriter's concert on Monday, held as part of her ongoing Hold On Baby Tour, she was joined onstage by Julian Casablancas of The Strokes to perform a cover of the band's 2005 alternative hit, "You Only Live Once."

"We're in New York, huh? We're in my hometown. So, maybe it's only fitting that we play a song by The Strokes," King Princess (whose real name is Mikaela Straus) told the crowd, receiving applause in return. "I mean, I don't know. I don't know who's gonna come out here, but..."

"Julian called in sick," joked the "Talia" musician, attempting to fake out the crowd before playing the First Impressions of Earth album cut's opening guitar lick. After singing the song's first verse and chorus on her own, King Princess was joined onstage by Casablancas, 44, who sang the next verse.

The pair duetted on the song's next chorus, during which Casablancas walked behind King Princess — strumming the song on electric guitar — and covered her eyes. "You're f---ing me up, bitch!" she playfully exclaimed.

After walking over to whisper something in Casablancas' ear, the rock star quipped, "Who the f--- was that?"

"Julian Casablancas, bitch," said King Princess with a laugh as he walked offstage.

Following the Radio City show, the "Little Brother" performer's Hold On Baby Tour is set to make stops in North American cities including Toronto, Seattle and Los Angeles before wrapping with a series of Texas shows through Nov. 5.

King Princess' sophomore album, Hold On Baby, was released in July and features a collaboration with the late Foo Fighters drummer Taylor Hawkins on a song titled "Let Us Die," which was recorded before his unexpected death in March.

Speaking to Entertainment Weekly about the track at the time, she revealed it was producer Mark Ronson who first suggested the idea. "Mark [Ronson] heard the demo and was like, 'I really think there needs to be a live drummer.' I agreed," she said.

Though both knew they needed a drummer, when Ronson suggested Hawkins, she could barely believe it. "Oh, my God, do you think we can get Taylor?" she recalled asking Ronson. After one call with the "Uptown Funk" hitmaker, Hawkins agreed.

"So we FaceTimed. He was recording in L.A., I was in New York, and it was crazy. I was in my childhood home — my dad's recording studio — listening to Taylor make my record better than I ever thought it could be," the "1950" singer said to the outlet.

Elsewhere in the interview with EW, King Princess said, "[Hawkins] added something to that song that goes so beyond just laying down a drum track. He really showed me a level of musicianship and also respect and kindness that I will never forget."

She also explained that speaking of the collaboration makes her emotional. "I didn't know Taylor that well," King Princess said. "I just felt so supported by his musicianship, and I can't believe I have the song."