The Coz (or The Cos) was a band that consisted of Greg Graffin, Davey Goldman, Greg Hetson and, shortly after Into The Unknown, also Paul Dedona. After a short while Paul quit, though, because Greg Graffin kept telling him to turn his amp down. Paul: "It just wasn't the same without Brett. He never told what to do ever and Greg and Davey always did. It was good to play with Greg Hetson. He was extremely experienced."
On other occasions they (members of Bad Religion) seem to deny the existence of The Coz. Jay: "The Coz was an inside joke of ours. It was in reference to "the cause" of punk rock, (or whatever you have) that we simply inserted Bill Cosby as the spokesperson for, called it "The Coz" and there you have it"