There was a full moon last night on Twitter, thanks to Justin Bieber.

The 18-year-old singer posted a revealing shot on his Instagram page on Saturday -- showing him pulling down his jeans to expose his butt while looking over his shoulder.

The photo was later removed for unknown reasons, but not before it had been commented on like crazy and liked over 15,000 times.

No reason why the Biebs decided to moon his fans, but manager Scooter Braun tweeted that it was some sort of prank.

"As a prankster you have to respect another good prank," he posted. "Only makes sense. #crackdealer."

The bare booty pic comes after Bieber's very public split with Selena Gomez.

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