What you see is not what you Observe

First Year MBBS students were attending their First anatomy class. They all gathered around the table with real dead body. The professor started the class by telling them two important qualities as a doctor. 

Sardarji, cool as a cucumber...

A Pakistani drinks his beer and suddenly throws his glass in the air, pulls out a gun and shoots the glass to pieces.

He says 'In Islamabad our glasses are so cheap that we don't need to drink from the same one twice.'