One of the few human beings who could make Robin Williams crack up beyond recovery.
His ad-libs were deadly to anyone playing opposite him. I remember one sketch wherein Winters was playing opposite a top comic (maybe Williams, maybe Carson; can't remember, Winters' career stretched so far back). Wartime, they were discussing serious strategy during lunch when the comic--who was holding a doughnut--delivered a semi-lengthy spiel about the urgency and near hopelessness of their situation. Winters stood quietly for the whole speech, staring at him, seemingly totally absorbed with the man's words. Then, with an absolutely straight face, gave a quick glance at the doughnut in the comic's hand and asked, "You gonna finish that...?"
The comic lost it completely.
Big Jon was gem.