Calvin and Hobbes by Bill Watterson for August 17, 1989
Calvin: There! A full pitcher of "Calvin's Curative Elixer"! We'll charge people a buck a glass and get rich! Hobbes: But that just dirty water from the drainage ditch! There are leaves in it! Calvin: "Fortified with clorophyll," we'll say. Hobbes: Nobody's going to pay to drink that! Anyone can see it's filthy! It's sludge! Calvin: Hmm... Maybe you're right.