Sometimes in a series, producers and show runners have certain supporting characters for a very specific purpose and then plan on ditching them. But once in a while, a supporting character becomes so popular that it gives writers a dilemma: what do they do with a character that was never intended to be on for more than a few episodes or a permanent supporting character that completely overshadows the main protagonist? It puts them in a tough spot because suddenly they’re scrambling for a storyline to keep viewers watching. See, it all comes down to ratings. Investors and show runners want to keep the level of viewership up but not at the cost of keeping someone else on the payroll. This is why a lot of fan favorites are “special guest stars” – it costs less than keeping as main cast. It throws the men in charge off their game because now they have a monster on their hands that both feeds and costs them.
This isn’t always the case though. Often times a supporting character is simply that - supportive. It wouldn’t cause a wave or threats of rioting if they were killed off or shipped away. Sure it would change the tone of the show a little but overall it wouldn’t be that bad.
That is so not the case for this list. In fact, many arguments could be made that these supporting characters not only improved on what was already a good foundation but actually sustain it. Supernatural was around for three high rated seasons before Castiel was brought in, but suddenly it wasn’t the same again when he was gone for a long time and it showed in the ratings. Violet Crawley is what keeps Downton Abbey grounded despite the fact that the series is really focused on the Crawley household. The house just isn’t the same when she isn’t criticizing everything. But like anything acting wise, it comes down to the right actor in the right role for magic to strike. Thankfully for these seven shows, it did.