Further proving that the Chabad Telethon has been firmly enshrined in American popular culture, Academy Award actor and comedic icon Robin Williams broke into an extended joke referencing the annual television program after his entrance as a guest of David Letterman’s “Tonight Show” Wednesday. After a series of ribs aimed at Letterman, who has not shaved his beard for the past two months, Williams remarked: “Nice to be here with you rabbi. How much money have we raised on the lovely Chabad Telethon?” ...