I'm not happy!!

You know the feeling, when you're in a bad mood and almost anything can make  you laugh...

Well, one day this guy was driving home from work in one of those moods, when ,while he was  trying to change the radio station, he rear-ended another car.  While he retrieved his insurance stuff from the glove  compartmen, he noticed that the driver of the other car was a dwarf.  The dwarf walked up to the driver and yelled,

"I'M NOT HAPPY!!"

With a big smile, the driver replied,

"Well, then which one are you?"