I'm going to say definitely Season 8, Episode 1 fits the definition of a true shark jump. A true shark jump is not one bad or below average episode, but an episode after which the entire series is never as good. The departure of Adam, Mary, Percival, and Nellie all at once was too much for Mrs. Oleson and it was too much for the viewer. Then you have the introduction of the evil Nancy, who is Nellie all over again and worse. Still an above average show, but I'm going to say after this episode never as good.