A mental hospital was critically overcrowded. The doctor decides to get all the patients seated in one large room to conduct a test to see how many they discharge that day.

At the front of the room the Doctors took some chalk and drew a full size door on a Blackboard and offered an ice cream to any patient who could open the door.

There was a mad rush for the door with the patients scratching a clawing at the door and the handle.

The doctors were disappointed, until they noticed a single patient who remained in his chair and was quietly chuckling to himself as he watched his fellow patients.

Encouraged that at least one patient could be discharged today, the doctors asked him why he wasn't trying to open the door.

The patient, who could no longer contain his laughter, shouted, "I've got the key!"