This is my favorite userpic.
When I was young, my mom stickered everything in the house with them. When something was bad, I would scrunch up my face and say, “Yuk!” because as far as I was concerned, that’s how it was spelled. Years later, I developed a habit of typing ‘yuk’ in chat/im/email in response to something bad. I guess it doesn’t carry the same meaning without the scrunched up face. Eventually, I was asked why I thought something was funny. Imagine my surprise to learn they’d never heard of ‘Mr. Yuk’, that he meant something was bad, and they thought I was implying a ‘nyuk nyuk’ slapstick humor.
So now I have the icon.