I thought about this tale while reading Mel Brooks’s new autobiography, “ All About Me!” My grandfather was the same generation as Brooks-both were born in New York in the nineteen-twenties and served in the Second World War-and my grandpa’s running joke was, essentially, the same one that Brooks deploys, with a thousand times the wit, in his comedy routine “ The 2000 Year Old Man” and in his 1981 film, “ History of the World, Part I.” Possibly more than anyone else, Brooks epitomized American Jewish humor in the twentieth century, much of which rested on the idea that it’s funny when a kvetchy Jewish guy shows up where he doesn’t belong, which is most places. When George Washington was crossing the Delaware and took a wrong turn, a voice piped up from the back of the boat: “Never fear! Arty’s here!” The day was saved. My grandfather Arthur Motzkin, a first-generation American Jew, liked to tell stories about his unlikely cameos in world history.