Krusty comes to realize that he can't find happiness in life because he never had a Bar Mitzvah, so he reunites with his father (a rabbi) and sets about having one belatedly.
Homer fills in for him on the TV show while he's away and becomes a celebrity for sharing his blunt observations with the world.
When Lisa convinces her dad to use his new pulpit to preach social activism, Homer's audience becomes bored and his fifteen minutes of fame dry up.