A guy was standing in the bus, when something knocks repeataidly on his shoulder. He turns around to find a strange shaped creature standing beside him.

The guy: Who are you, you scared me?

The creature: Dont be afraid, I am your friend Mac from mars and I am on a visit to your planet

The guy: Excuse me friend, but what are these four holes in your face?

The creature: They are my eyes.

The guy: And what are these eight buttons?

The creature: They are my ears.

The guy: But excuse me brother, how you are macking sex to each other?

The creature: By knocking on the shoulders of others!!!