North West's Natalie Nunn Halloween costume caught the rapper's eye ... and she returned the favor by dressing up as the child star.

The "Bad Girls Club" alum shared a video on Instagram Thursday night where she lies down on a bed ... and wakes up with blue hair in pigtails, spiked bracelets, and black acrylic nails.

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Natalie puts on a shocked face ... covering her mouth with one hand in a pantomime of a classic North mannerism.

She captioned the post, "Uno reverse 🔄 @northwest."

As we reported ... North dressed up as Natalie in a video she posted -- with a sharp elongated chin, a "Baddies" diamond chain and straight black hair.

Clearly, Natalie loved it ... though she's a little late to the "dressing like North" party. NW's famous mom -- Kim Kardashian -- already dressed up as her earlier this week, and she totally nailed the look, too.

The real question ... who wore it better?