Think they added Joe for the hard rock audience. I also make a joke that they fired Joe but he just kept showing up, Joe was heavily into drugs at the time. So he did not realize that he had been fired. One day Don took Joe aside to explain he had been fired. Joe kept going ok but can I still play with the band. Finally Don said ok you can play but no paycheck. Joe replied OK, but can I still have a free tour t shirt? Don laughed and said ‘sure’.
Joe was pretty funny in this clip from The Drew Carey Show
https://www.youtube.com/watch?v=BJTqvNLQlG0