The pun here is that an "I.C Wiener" (I.C being a pun for 'icy' and wiener being a slang term for a penis) is found in a cryogenics lab, where people are frozen.
You may wish to note that in the original storyboards, the Cryogenics Lab was going to be a division of Birdseye, Inc., a company famed for its frozen products and the joke name on the slip was going to be "W. Disney" rather than I.C Wiener, riffing off the fact that Walt supposedly had himself frozen after death.