100 episodes

100 episodes is considered to be the magic number at which point many television series (which usually run 22-26 episodes per year) are viable for TV syndication, usually translating to the start of the fifth season.

Many fans of plot arc oriented series - rather than highly episodic ones - consider this the critical time when a show might be growing stale or starting to lose its audience, especially if it is reported to be picked up for more seasons. This can happen either because a series is changing its tone 'excessively' or sometimes not changing enough.

Series accused of the 100 Episode curse include X-files, Angel, Buffy, Sailor Moon etc. Series such as Babylon 5 are excluded, as its fifth season is an intentional and specific ending.

External Link This link needs an explanation. It goes back to an episode of "Happy Days" in which Fonzie was water skiing and jumped over a shark. The series had been amongst the most popular in the US at that time. This single episode was seen as containing material that went beyond what was interesting or helpful to the series, and from this point onwards a decline was seen at least critically.

Since that time jumping the shark has come to mean the over extension of what a TV show can believably do, or, more generally, the moment at which a show begins to go steadily downhill.

• jumptheshark.com chronicles when television shows go stale