Outnumbered Sibling: Bart started feeling this in this episode. He even imagined what his future would be like if his attempts to trick his parents in having another child resulted in a third girl.
Later, Charlie (the orphan acting as Bart's brother) is adopted by a couple with six daughters.
Shout-Out: The scene of Bart telling his friends about his baby brother dilemma looks and is "animated" like South Park.
Siblings Wanted: Bart tries to convince his parents to have another boy, but gives up when Marge points out that even if she and Homer did want another child (which they don't), it might end up being another sister.