"We always had to make a conscious decision to make the same movie over again, only each one would be slightly different," says Steve Miner, the director of the second and third Friday the 13th installments (and associate producer of the first), in the franchise's oral history, Crystal Lake Memories. Indeed, by 1982's Friday the 13th Part III, the series was already repeating itself: once again, we watched a formerly bullied giant mama's boy stalking dumb kids in a rural setting, killing some in ways he had killed their predecessors (through-the-bed stabbing from below got a reprise). The climax virtually repeated that of the first film's except it was Jason who was doing the slaying and his now-decomposing mother who did the final-scare popping out of the water. They just traded roles, of course — shifting bodies around was business as usual.

As for the slight differences, there was comic relief via a Tommy Chong-esque hippie character and his girlfriend; it acknowledged the existence of black people, one of whom plays a crucial role in the salvation of the final girl; it was shot in 3D and it is the Friday the 13th in which Jason found his hockey mask. (He made a barefaced cameo in the first and wore a burlap bag in the second.) The last was a tweak that would result in iconography.

The third entry is when a horror franchise becomes a franchise. It is when mythology intensifies, when the bludgeoning becomes a conscious rhythm, when the audience becomes devoted, when those on the outside start making jokes about the never-ending sameness of an entire genre. It's when a possibly decent concept becomes stretched into cinematic taffy – even the best ideas have trouble withstanding the weight of themselves by the third time around. Look what happened to The Godfather.

I often find myself attracted to Part 3's, especially when it comes to slasher films. Sometimes it's because they are great, but more favorably, it's when they are train wrecks (appreciating badness is a key component to horror-movie adoration). The first three Friday the 13ths are virtually interchangeable, but by Part III, there is a heightened efficiency to the setting up and offing its dumb kids, a kind of elegance within the sleaze. 1987's A Nightmare on Elm Street 3: Dream Warriors, on the other hand, refreshes with series with heightened creativity. The cartoonishness of a metal-clawed raisin can no longer be contained and in 3, Freddy Krueger becomes at least as campy as he is scary. He bickers with Zsa Zsa Gabor, plays puppeteer using a kid's tendons, takes on a D&D-inspired wizard and momentarily becomes a hot '80s female pin-up who spits binding tongues after she seduces a kid. The one-liners became punchlines: before pulling a compulsive TV watcher through a television set, Freddy proclaims, "Welcome to prime time, bitch!" Child murderer or Alf?

Co-written by Wes Craven, who created the series and directed its first installment, Nightmare 3 justifies its own existence by filling in its legend with back story on Freddy (he was conceived when his nun mother was gang-raped, our inquiring minds learn), the first film's protagonist Nancy, who ends up dying, and the "Elm Street children" – the group of kids Freddy stalked because of their parents' involvement in his murder. There is a sense of accountability there, a determination not to be just another mindless blood bath. Craven wanted to make this the franchise's last installment and it feels like a purging of ideas. He had, in fact, initially proposed a meta-setup in which actors in a Nightmare film were being stalked by Freddy Krueger a la the later, actual final installment, New Nightmare. Though inventiveness came in flashes through the rest of the franchise's duration, it would never again reach 3's consistency.

If Friday III already came with its legend filled in and Nightmare 3 was devoted to fleshing it out, 1982's Halloween III turned the very notion of a franchise on its head. Halloween was originally envisioned to be an anthology series, with each film unrelated. But that didn't happen and Halloween II picked up immediately after the first one ended. After spending two movies with Michael Myers, John Carpenter and producer/co-writer Debora Hill haphazardly decided to enact the anthology idea for Part III, which has no Michael Myers or nothing to do with the two films that preceded it. Basically, they served bacon twice and then switched to tempeh but continued calling it bacon. The result is the wacky Halloween III: Season of the Witch, an enjoyable tale of witchcraft meets '80s technology in which Halloween masks were rigged to kill the kids who donned them via a strobing commercial (if it didn't end up murdering them, at least it would induce a seizure). The resulting outpouring of snakes and crickets is the most ghoulishly abstract imagery the franchise ever offered.

Not that it mattered — Halloween III was a huge flop. People wanted their bacon, damn it, and when they finally got it back with 1988's Halloween 4: The Return of Michael Myers, they rewarded it with box office numbers that more than tripled its $5 million budget. Somewhere between Friday III's inertia and Nightmare 3's ingenuity, Halloween 4 plays up the boogie man imagery by having Michael stalking an actual child (his niece, Laurie Strode's daughter Jamie played by future scream queen Danielle Harris) and getting more disgusting with his murdering, thus further betraying Carpenter's mostly bloodless original masterpiece. Early on, Michael puts his finger through a guy's forehead in a scene that resulted from an additional day of "blood filming" after the franchise's new owner, Moustapha Akkad, decided an early cut was too clean. The boogie man was starting to act a lot like Jason Voorhees, the thread of influence was becoming tangled (Halloween led to the slasher craze of the early '80s and the likes of Friday the 13th, whose popularity then influenced the Halloween franchise).

Tackling a Part 3 is a big responsibility in terms of both upholding a franchise and moving it forward. It is where Saw became operatic and where Paranomal Activity became visually inventive within its self-imposed lo-fi constraints. Meanwhile, third installments like Day of the Dead and Leatherface: The Texas Chainsaw Massacre III were released in formats that greatly deviated from their conceptions because of over-ambition. Child's Play creator Don Mancini admitted that he ran out of ideas after the second movie, and the resulting third was his least favorite installment. Number 3 is almost always what makes or breaks a franchise that is inevitably past its prime – a kind of meta experience itself, it's when we watch series begin to die. The question is whether the death will be slow or fast. But then, that's usually how it is with horror.