Family Guy (1999)

S4E22 Sibling Rivalry

After Peter undergoes a vasectomy, he finds himself with no interest in intimacy. Meanwhile, as Lois starts to put on weight, Peter suddenly takes notice of her again. However, things take a turn when Lois's unhealthy lifestyle leads her to suffer a heart attack. To save her, the surgeon has to remove excess fat to access her heart, bringing her back to her usual weight. In a separate storyline, Stewie's half-brother Bertram makes a comeback, leading to an epic showdown between them for dominance over the playground.