Calvin and Hobbes by Bill Watterson for August 23, 1990
Calvin: There! I finished our secret code! Hobbes: Let's see. Calvin: I assigned each letter a totally random number, so the code will be hard to crack. For letter "A", you write 3, 004, 572, 680. "B" is 28, 731, 569 1/2. Hobbes: That's a good code all right. Calvin: Now we just commit this to memory. Calvin: Did you finish your map of our neighborhood? Hobbes: Not yet. How many bricks does the front walk have?