Sustained success for a TV show isn't always easy. Consistent quality is never a given -- unless the show has the words Law & Order somewhere in its title -- and even the most critically-acclaimed, ratings darlings are bound to hit a slump somewhere in their run. When that happens, it might be necessary to inject some new blood into the mix.
The same can be said for a show that hits the skids right out of the gate. There are plenty of examples of soon-to-be iconic TV shows that didn't quite catch on with the public until a couple of seasons in. What changed? Sometimes just a cast member or two.
Getting audiences to fall in love with a new character can be tough, as well, and it's certainly no guarantee that this fresh face will revive a show all by themselves. In fact, they may just ruin the show once and for all. (We call this the "Cousin Oliver Syndrome.")
But every once in a while there comes a knight in shining prop armor -- a savior backed by the majestic sounds of a laugh track -- riding onto set in a white trailer to save the day. These are those characters.