It’s one of Hollywood’s best-known unwritten rules: Milk an idea for as long as you can.

That's how the world was given an endless supply of sequels and reboots, with studio executives eyeing every film as the possible start to their next great franchise.

Of course, at some point, the quality of these cinematic follow-ups begins to dwindle. That’s not to say that producers pull the plug at the first sign a franchise is faltering. Far from it. You can count on one hand the number of franchises that ended at exactly the right time. (Back to the Future immediately comes to mind, but beyond that, we’re stumped.)

The allure of building upon a brand-name film that fans are already familiar with is simply too strong. That’s why studios return to franchises years – and sometimes decades – after they’ve begun.

UCR combed through the motion-picture history books and found 42 instances where great movie franchises went bad. In some cases, the offending film marked the end of the brand. In many others, it was just a blip on the radar, a momentary lapse in quality or popularity that would soon be rectified by another installment.

Our list below spans all types of films – including comedy, drama, action, horror and more. Interestingly, despite the disappointing quality of these films, the vast majority still turned a profit. For the sake of this exercise, a franchise was defined as any movie series made up of three or more films.

Grab your popcorn and prepare to be underwhelmed.

42 Times Good Movie Franchises Turned Bad

You can count on one hand the number of franchises that ended at exactly the right time.