Jimmy Fund 

Defining or explaining the meaning / origin of a topic, only to shortly find out that you are completely incorrect and had no idea what you were talking about.

He explained to us the historical origin of charity signs around the park, only to find out with a quick search that he had pulled a Jimmy Fund and was completely wrong and failed in every way.

Jimmy Fund by bigjackass March 15, 2010

jimmyfun 

A very handsome and brilliant man with a strange attraction to cars of different kinds. He is sweet, funny and witty, and is often seen with a nicely shaped beard.

"Oh man, look at that sexy car!"
"Haha, you're such a Jimmyfun!"

jimmyfun by Gladioli March 30, 2005