People are being plagued by an ad for a sexy butt-flap onesie from unknown fast-fashion brand IVRose following them around the internet.

Today’s typical onesie wearer has more of a sense of fun, according to Masters, who said men in California will go bar-hopping “with funny underpants on underneath and the butt flap open.” ...

In fact, the actual name is “ Plain Functional Buttoned Flap Adults Pajamas,” and they’re sold by an e-commerce retailer named IVRose for the low, low price of $26.99 ...

The ad is meant to promote the Plain Functional Buttoned Flap Adults Pajamas, priced at $26.99 (with a wealth of discounts available if you buy more than one pair).

Hold on to your butt flaps — adult onesies are having a national moment. And it’s all thanks to the Chicago Cubs, who celebrated Jake Arrieta’s no-hitter against the Dodgers on Su… ...