Doonesbury by Garry Trudeau for February 10, 1972
George: You know what bothers me, B.D.? - It's impossible to see the enemy.. B.D.: Don't worry, George, he's out there...as a matter of fact, there's Charlie now! Better get down, man....that's another thing! Why do we always call the enemy "Charlie"? "Charlie" is such a boring name! Why not "Arnold," or "Seymour," or "Peabody"? B.D.: You meathead.