The Chrissy Snow Syndrome

Generallt occurs only on long-running TV shows, but there are exceptions. When writers accentuate the traits of formerly likable characters in later seasons so that the characters become complete stereotypes. The eponymous Chrissy Snow (Suzanne Somers) on Three's Company was the trailblazer - she came blonder, her do became more implausible, her intelligence level plummeted, and her laugh became unbearable after season 1.

Friends was a fine show until the Chrissy Snow syndrome struck again. Monica became an anorexic, OCD shrew. Ross became a simpering buffoon. Phoebe became - eh, who cares.