The logic behind the spin-off is very sound. Take a beloved character or concept from a pre-existing series and create an entire new show. You have an established character or brand and thus a built-in fan base. It makes perfect sense, no?

Unfortunately, the reality of the situation is not quite that simple. Certainly there have been spin-offs that attracted both fans and critics and managed to create a legacy all their own. Shows like "Frasier," "Angel," and "The Jeffersons" instantly come to mind. But for every successful spin-off, there have been dozens of miserable failures...