The actress that plays Wendy is actually in a relationship with Jim Jefferies. They have a son named Hank.
Walter Nugent, Billy and Steve's father, was portrayed by Warren Kirkpatrick in the pilot only. John Ratzenberger took on the role late in the first season and for the remainder of the series run.
Jim tells the story played out in the Pilot in his 2010 stand up special 'Alcoholocaust'.