Three easy pieces

A man walks into a bar and orders a sandwich and a pint of beer. After chewing on the sandwich for a while, he angrily addresses the bartender :

- I want my money back. There's sand in my plankton sandwich.

(Actually, there wasn't any. I don't know why he said that.)

* *

The other day a man walked into a grocery store and went to the vegetable section. He saw some broccoli and instantly produced a revolver from his vest and shot several times at it. The clerk managed to overcome his fright and asked the man :

- Are you out of your mind? What the hell did you do that for?

- Sorry. I was aiming at the cabbage.

* *

Yet another man walks into a doctor's office.

- Are you a doctor?

- Yes, I am.

- Why do humans sleep?

(I suppose the man believed that doctors should have an answer to every question - that's why this joke is hilarious.)