After a pregnancy scare Lois makes peter get a vasectomy. Before his surgery he decides to donate sperm. A lesbian couple, wanting a baby uses Peters sperm to have a child of their own. The lesbians gave birth to peters son and named him Bertram, Stewies half brother who was shown in the episode "Emission Impossible." Shortly after Peters vasectomy he loses his sex drive and Lois gets frustrated and starts excessively eating and becomes obese.
Meanwhile Stewie and Bertram fight over playground turf to become the playground rulers. The pair have humorous fights which involve helicopters and aeroplanes, sword fights, and biological warfare.