Even though the kids' bathroom does not have a toilet, you actually hear Bobby flush the toilet when Bobby and Peter fight and make a tape line in the middle of the room and Bobby points out to Peter that he is on the side with the bathroom.
After being trapped in the closet, Bobby talks about a fire by spontaneous combustion, choking on smoke and being rescued at the last minute. A year later, exactly that would happen to Mike Lookinland in "The Towering Inferno" (1974).
In the opening scene of S5:E7, Marcia Gets Creamed, Peter wears a multi-color shirt. He again wears the same shirt in S5:E8, My Brother's Keeper, during the dinner scene.
The title comes from the Bible story of Cain and Abel, and the common expression: "I am not my brother's keeper".