20 Pints Of Guinness

A man walks into a pub and gets the barman to pour twenty pints of Guinness and line them up along the bar. The guy then takes the first pint and necks it in one go.... then the second...then the third and then the remaining 17 pints, without a pause. He pays the barman, and just turns and walks out.

Two men sitting in the corner of the room watched this whole episode and one turned to the other and said "I'll bet he drinks Carling Black Label."