Forget planking, coning, swatting and all those celebrity trends and pranks that go viral and entertain us for 10 minutes. One Direction cutie Louis Tomlinson was the victim of an old-fashioned prank when someone dared to slap him on the butt after a swim. LT, usually possessed of a terrific sense of humor, was not pleased when someone had their way with his bum.

He was fresh from a swim and wearing a wetsuit, so at least the gutsy person, likely a Directioner, didn't get a handful of skin or leave a mark.

You can see the errant hand touch his rump below.

And then his totally irritated reaction, which, we admit, made us giggle. A lot.

What is it with One Direction and their rear ends lately? First, Liam Payne's boxers were jacked after a swim. Now, LT gets swatted on his derriere.

Directioners, while we can understand the desire to touch a member, please be respectful of their personal space and keep your hands to yourself.

Watch Louis Tomlinson + Liam Payne Frolic in the Ocean