The first 20 minutes of the director Kyle Mooney’s “Y2K” are so densely packed with references to turn-of-the-millennium pop cultural ephemera — AND1 apparelpokerstars, “That 70s Show,” devil sticks, Tae Bo and the Dancing Baby, to name a handful — that I was exhausted by nostalgia before the end of the first act.

Mooney’s ordinarily eccentric, heavily ironic sense of humor, honed over many years on his cult-favorite YouTube channel and later on “Saturday Night Live,” seemed to have been replaced by something more cloying and conventional, where simply reminiscing about 1999 was a substitute for actually writing jokes about it. (Mooney and Evan Winter penned the screenplay.) Where was the genius behind such classic sketches as “ball champions,” an early forerunner of “How To With John Wilson” and “I Think You Should Leave”?

But then the movie takes a sudden, jarring pivot, and Mooney’s unique sensibility aggressively (and thankfully) reasserts itself: A familiar story of teenage slackers at a New Year’s Eve party transforms into an anarchic, over-the-top Armageddon picture, as the “Y2K problem,” the computer coding crisis that incited much fear on the eve of the year 2000, turns all electronics evil and bloodthirsty at the stroke of midnight. A beard trimmer leaps into jugulars, a VCR shoots tapes like a cannon, and the carnage of consumer goods is nasty, gory and cruel, with a darkly comic mean streak that recalls Joe Dante’s “Gremlins.”

Jaeden Martell, Julian Dennison and Rachel Zegler, as the teens tasked with thwarting the apocalypse, make charming heroes — but it’s Mooney himself, as the loquacious stoner Garret, who is the film’s dopey MVP.

Y2KRated R for strong languagepokerstars, frequent drug use and intense graphic violence. Running time: 1 hour 33 minutes. In theaters.

• Review
• Like
• Dying
• pokerstars
• Y2K