Once upon a time there was an evil mathematician who started differentiating things.

Once upon a time there was an evil mathematician who started differentiating things. He pointed at his couch and yelled I differentiate you!, and it differentiated. He pointed at the mailman and yelled I differentiate you!, and it disappeared. He pointed at the shop across the street and said I differentiate you!, and it exploded. He was finally subdued after a long struggle and taken to court. To keep him from causing more chaos, he was drugged and unable to speak. The judge found him guilty, and was about to sentance him when the drugs wore off and he started differentiating things again. He differentiated the bailiff, the judge, and the jury, when someone came up behind him and put his hand on his shoulder. The evil mathematician pointed at the man and yelled I differentiate you!, and nothing happened. He tried to differentiate him a second and third time to no avail. Finally, he looked at the man and said, What's going on? Why won't you differentiate? The man looked back and said, You can't differentiate me -- I'm e^x.