Charli XCX Brings Down The House In Times Square After 'SNL' Appearance

Charli XCX is taking the Big Apple by storm ... putting on a surprise performance Monday after her appearance on "Saturday Night Live" over the weekend.

The pop star popped up onstage in Times Square last evening just 30 minutes after the H&M clothing company announced that Charli would be putting on a gig. Charli did the show to promote her new holiday fashion line for H&M.

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She cranked out several of her hits in front of a packed crowd, including “360,” “365,” and “Apple.”

Before Charli appeared, several large digital screens wrapping around the stage turned into the cover of her famous "Brat" album.

Check out the video ... one of the screens starts flashing as two doors open and Charlie steps out onstage with everyone in the audience going nuts.

Throughout the clip, the audience is having a blast and so is Charli who gives a very leggy performance.

As you know, Charli hosted 'SNL' last weekend and showed off her acting chops in a sketch called "Babymoon," which was a follow-up to Ariana Grande's popular skit, "Bridesmaid Speech," from last month.