I cannot say if this moment happened, but the comics were given two restrictions. They could not, in any way, touch the players, and also they could not talk to the player, beyond asking yes or no questions.
The contestant also had to maintain eye contact with the comic, and an official "laugh" was the contestant opening his mouth or showing his teeth.
Bert Convy was on the show as a special guest, and Garry Shandling made him laugh before he could finish the joke. When Garry said "Jewish Country Safari" that was enough for Bert to laugh before 5 seconds were up. (Steve Beverly incorrectly gave another comic the credit for the joke on his site)