Sitcoms to drama - A tv show's big change

[IkeaBoy]

We know about M*A*S*H, the preminent show that started as a funny sitcom and turned into a suicidally depressive drama with no charm but what are some examples of this massive change you remember.

* Boy Meets World: kid grows up with wacky character, enters high school and his entire world turns teen angsty with an abused best friend and crap like that.
* Dharma and Greg: Stupid free spirit, straitlaced husband and then they start fighting and she breaks her neck in a car accident.