This has got to be the most evil prank you'll see today

It's so evil, it's got a screw loose.

Redditor _janson has loaded a YouTube clip of a deliciously naughty prank.

Somoeone's brother is on the slingshot ride at the fairground, already looking fairly nervous about it.

It's poised to start when he hears something drop and turns to see a friend holding a screw.

What the...?

H/T: Reddit.