He fired me 'cos he was jealous!

Two friends were talking about recent events in their lives.
One asked the other "So Jack, why did your boss fire you?"
Jack replied, "Cos he was jealous!"
Bill, "That sounds weird. How can your boss be jealous of you?"
Jack answered, "Well you know how a supervisor is always standing around and watching others do the work. My supervisor got jealous. People have been making the mistake of assuming that I am the supervisor. He couldn't stand that!"