There is no quaternary word to correspond to trilogy. Many of the best modern movies were trilogies: the "Godfathers," the "Back to the Futures," the "Star Wars" and "Indiana Jones." But they always stopped at three.
The next year in movies will herald, hopefully, the competent and resourceful fourth film in a series: "Star Wars." (Which, technically is the series' first film, since it's a prequel.)
Last year a fourth "Alien" film, "Alien: Resurrection," was the harbinger for a new era in corporate filmmaking where a successful movie can be Xeroxed into infinity.
This isn't to say that there weren't movie franchises which boldly crossed the triple line in the sand. But look at the movies which did: "Nightmare on Elm Street," "Kickboxer," "Friday the 13th," "Batman," "Halloween," "Silent Night, Deadly Night," "The Howling," "Police Academy," "Leprachaun," "Critters," "Meatballs," Superman" and "Rocky."
Half of these lost the sparkle that made their characters so appealing; the other half discarded the characters altogether and recycled the name only.
Now, there have been movie series that have successfully gone past three before: the "James Bond" and "Dirty Harry" movies. But both are archetypical characters; they will not change and grow from film to film. A true sequel takes the characters' stories and updates them.
If you didn't see "Alien: Resurrection," (the fourth "Alien" movie) you're not alone. It wasn't a huge success, but it wasn't a flop, either. The Ellen Ripley character, who died at the end of "Alien 3," was cloned, along with an implanted alien. She had to get across the alien-infested spaceship before it self-destructed. It wasn't the best in the series, but it broke the fourth-movie curse.
There are two different aspects to the sequel business which should be separated. The business of movies says to go with what works. That's why there's serious talk of "Titanic 2." Yes, "Titanic 2." Maybe the liquid metal Titanic-1000 will come from the future and try to sink Rose again.
"Home Alone" had two sequels, even though the story was so wrapped up at the finale it didn't need a sequel. But the first was successful, so the second was made. Same thing with "Weekend at Bernie's," "Speed," "Under Siege," "Blues Brothers," "Mortal Kombat," "Wayne's World," "The Poseidon Adventure" and the downright wretched "Highlander" series.
"Scream 2" had plenty of self-depreciative references to how all sequels aren't as good as the first movie. And true to form, "Scream 2" wasn't as good as the first.
If a movie makes money, it's unbelievably easy to get a sequel made. There is a sequel to "The Fugitive" coming out, except Harrison Ford's not in it. And look for "Species 2," even though most of the cast died at the end of the first movie.
That's one aspect that contributes to bad four-film series; they'll continue to make films regardless of quality. Once the ball starts rolling, it doesn't stop until it flops at the box office. Studios will keep on doing something until they get it wrong.
The other aspect is the mechanics of storytelling. The characters go through a change by the end of the story. Then they go through a second change at the end of the second movie which related to the first movie. By the third movie, the characters can't be changed too much or else they won't be the same characters they once were.
So they have the same thing happen to them in the third movie as in the first. Check out "Back to the Future III," "Godfather III," "Return of the Jedi." The original conflict comes back.
That leaves no place for the fourth movie; the story has come full circle. There's no where else for the story to go without repeating itself for a third time.
The "Alien" movies solved the problem. The first movie was science fiction, the second action, the third horror and the fourth was really a disaster movie. Instead of trying to reinflate the conflicts of the previous movie, they take the story in a strong new direction.
The fourth-movie high-tide has begun to lap at the shores of cinemas. This summer: "Lethal Weapon 4." In production: "Die Hard 4" and that "Star Wars" prequel.
Think about your life; it has been a romantic comedy, a terse drama, a slapstick romp, a tragedy and a family epic. Yet it's always been you in the center of everything. Characters are elastic enough to be in more than one genre of movie, because people are pliable enough to be in more than one type of life.
Hopefully Hollywood will realize this before "Weekend at Bernie's 3" or "Power Rangers 3" hits theaters.