This article is from the The Complete Guide To Hack Stand-Up Comedy, by Steven Rosenthal and Steve Silberberg (email@example.com) with numerous contributions by others.
Andy Kindler's magazine article THE HACK'S HANDBOOK says that this bit
boils down to "Dogs will do anything, cats don't care. Example: Cats won't
fetch a bone. 'You fetch it. I'm getting something to eat. And take away
this cheap shit and get me some real food.' Dogs will eat lard and Spam!"
The whole pet thing has been a road comic's staple bit for years now. Don't