During many of the earliest episodes of the show, Joe would randomly feign rage toward Lars, lambasting him and demanding that he stop talking by yelling "Shut up, Lars!" or some variation. After this, he would usually give an overstated apology for his behavior.
Occurrences of this "gag" would become increasingly dramatic, and the apology more and more overstated. At times, he could come across as borderline sociopathic.
This gag has mostly been abandoned. While Lars and Joe still engage in exaggerated banter, they now tend to be far more creative with it.