The hijinks took place Monday night at the Hollywood Palladium as Lizzo performed the call-and-response "Gigolo Game." The chart-topping singer and rapper, 31, invited the "Home Alone" star, 39, to join her onstage to bust a move.
"When @lizzobeeating asks you to do a silly dance... You get up there and do a silly dance," Culkin captioned a video of the fun.
In the clip, Lizzo asks the actor, "Hey, Macaulay, are you ready?" After replying with a boastful "Yeah," Culkin gamely launches into an old-school Sprinkler dance, holding one hand behind his head and his other arm outstretched while spinning in a circle.
Lizzo and her backing dancers cutely follow Culkin's lead and do the dance alongside him.
Afterward, Lizzo tells the crowd to "make some noise" for the actor and the two stars embrace.
While the pairing may have surprised fans of both entertainers, it turns out they've been pals — and musical collaborators — for years. Lizzo toured with Culkin's band, The Pizza Underground, in 2014, and later name-dropped the actor on her feminist anthem "Like A Girl."
Culkin, meanwhile, showed his love by appearing in the video for Lizzo's single "Faded."
"(Culkin’s) really supportive and one of the best people I’ve ever met in my life," Lizzo told British music mag NME last year. "Not just because he’s Macaulay Culkin, but because he is an awesome human being."