Dennis the Menace began on March 14, 1951 (four months after Ketcham's friend and colleague Charles Schulz started his own historic comic strip). He went on to become the second most popular cartoon kid in the world -- after Charlie Brown, of course. Dennis the Menace first appeared in 16 American newspapers; by the end of 1951, he was appearing in over a hundred. The reason for Dennis' success is easy to figure out: It was one of the most...