Billy Miller appears only in Medicinal Fried Chicken, in which he appears as the KFC trafficking lord (a play on a drug lord) and takes his business very seriously. He hires Eric Cartman so that he can repay his debt for the popcorn chicken he ate. Soon after sending him to set up a deal with Colonel Harland Sanders, he is overthrown by Cartman. The Colonel sends his goons to kill Cartman and his group, meanwhile killing Billy's mother, Mrs. Miller.
Billy has a very business-like personality and seems to understand what it means to be trafficking chicken. He seems to prefer solving problems, such as debt, in a business-like way and is shocked by Cartman's ridiculous order of 10,000 boxes of chicken. He releases that he "can't move that kind of chicken", acting like a stereotypical drug lord. "I'm not making any money here, I'm losing it! I have to pay for more security, I got the cops up my ass and I have to hire these sorters to get the chicken ready for distribution!".