Television spinoffs get a bad rap. When word comes down that a new series will launch with existing characters in lead roles, there’s a tendency to assume the finished product will be a watered-down and unnecessary cash-in on previous success. But if you take a gander at the history of television, you’ll find that some of the most beloved series of all time are spinoffs — including many that you may not even remember as spinoffs.

In this week’s episode of Vulture’s “Secret History of Television,” we look at the way spinoffs have evolved over the past 60 years, break the concept into two categories, and propose a reason why spinoffs might be on the decline (at least in scripted TV). And, who knows? If enough people watch this episode of our series, maybe we’ll start a new companion. (“Vulture’s Even Secreter History of Television,” perhaps?)

Come back Wednesdays for more episodes, and check out our past installments on topics like “lesbian-kiss episodes” and swearing.