Well geez sherlock, aren't they all? :P
"Genny Screamers" refers to the screaming speed at which you must run to the john, the scream of pain as your bowels evacuate until it seems your tonsils and sinuses are enroute, and the scream of the next person to enter the john when the wall of aroma strikes them.
All of the above entertainment is caused by consuming copius quantities of Genesse Cream Ale. It is something everyone should live once