What is a wet willy?

A wet willy is a prank in which a person sticks a wet finger into someone's ear, usually by licking their finger first. This act is typically done to annoy or surprise the recipient and is considered impolite or disrespectful. It is often performed as a joke among friends or siblings. The term "wet willy" is believed to have originated in the United States in the 20th century. While some people find it harmless and funny, others may find it gross or invasive.