Calvin and Hobbes by Bill Watterson for March 25, 1987
Calvin: Well, what do you say? Would you like to be transmogrified? Hobbes: I don't think so. Being a tiger is my area of expertise. Calvin: Don't be scared. The process is instantaneous and completely painless. Just think! WIth the push of a button, you could be a 500-story gastropod - a slug the size of the Chrysler building! Hobbes: Gosh, how can I refuse? Calvin: Well if you don't like that, be something else! I don't care!