Hahaha!
In ninth grade I was not paying attention in Algebra and drew a duck in my notebook. I am NOT a good artist, at all, so when making the circle for the duck's head I accidentally made what looked like an angry eyebrow. The thought of an angry/evil duck made me happy so I added a pitch fork and devil horns to match the angry eyebrow.
It's been my user name ever since and whenever given a pencil I usually replicate the duck before doing anything else. It's kind of like a signature. But unofficial. Because they don't let you sign things with crappy pictures.