Flanderization

Many fans say that season 5 was the beginning of its downfall as Flanderization occurred. JD went from being a little emotionally needy to a whiny man-child and Elliot became every negative stereotype about women instead of her usual neurotic but lovable self.

Part of the decrease was a "Flanderization" of the Rat […] his characteristics became exaggerated to the point that he seemed to me to be approaching self-caricature […] and Harrison's writing quirks began to dominate the story, rather than merely accent it.