Calvin and Hobbes by Bill Watterson for March 22, 1991
Calvin: I've got to say, Hobbes, I've really perfected my old duplicator this time! Hobbes: I'll grant it needed perfecting. Calvin: It was so simple to add an ethicator! I don't know why I didn't think of it before! Now, instead of making a complete duplicate of me, I've made a duplicate of just my good side! He does all the work and I get all the credit! He's a total sap! I know! I know the answer! Miss Wormwood: You've gotten so many, let's let someone else try this one, ok, dear?