I started an argument with him about whether or not it was raining. Then he used Rozenism to make it seem like getting wet from water falling out of the clouds actually meant that it was dry.
(Latin) Literally "Not Worth a Rat's Ass," the slogan of the Tunnel Rats, who were either U.S. Army combat engineers or infantrymen of small stature who cleared the extensive tunnel network of the Viet Cong during the Vietnam War.
Willy wore a patch with the saying "Non Gratum Anus Rodentum" on his field jacket. This indicates that he was a Tunnel Rat during 'Nam.