Is the Film Trilogy Going Extinct?

Ice Age: Continental Drift broke ground as the second-ever animated "fourquel" to hit theaters. The Lord of the Rings films are getting a prequel. Is The Dark Knight Rises a final gasp of the three-movie format?

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Clockwise from top left: the first, second, third, and fourth Ice Age movies. (20th Century Fox)

"Two million years ago, one Earth-shattering event changed everything," says the trailer for Ice Age: Continental Drift 3D, the animated film that was No. 1 at the box office this past weekend. But regular moviegoers may feel like they've spent time with Manny, Sid, and Diego a good deal more recently—and a good deal more often. The first Ice Age hit theaters just 10 years ago, but three sequels have already followed, presumably to answer all the lingering questions that the first film left behind. The Ice Age movies have never been critical darlings; the third installment, Dawn of the Dinosaurs, earned just 45 percent positive reviews on Rotten Tomatoes, and Continental Drift 3D is even worse (no matter what Atlantic critic Chris Orr's kids say). But as the fourth movie in the Ice Age franchise, Continental Drift 3D occupies a key place in an accelerating Hollywood trend: the decline of the once-iconic trilogy format—which has marked series as acclaimed as The Godfather and as profitable as Star Wars —in favor of an open-ended franchises that can be revisited for more films (and more money) for as long as studios sees fit.

Four-film franchises (or "quadriologies") have technically existed since the early days of film, but they're considerably rarer than trilogies. There are good reasons for that. By the time a series reaches its fourth movie, audience and critical fatigue with the franchise tends to have peaked. It wasn't until last year's Mission: Impossible - Ghost Protocol that a "fourquel" earned franchise-best reviews. And even more tellingly, the list of once-venerable franchises whose fourth installments were also their worst­-reviewed—which includes Indiana Jones, Batman, Terminator, and Pirates of the Caribbean—is considerably longer.

What accounts for the vast gulf that separates the Hollywood trilogy from the Hollywood quadrilogy? In Hollywood, there's one key difference between the creation of a trilogy and the creation of a quadrilogy: planning. As a general rule, trilogies tell one long, continuous story, with each part necessary for the whole. The original Star Wars can theoretically stand alone, but its greater plot emerges in the second installment, The Empire Strikes Back, which ends on a cliffhanger to be resolved in the final film, Return of the Jedi. Many subsequent franchises, including The Matrix and Pirates of the Caribbean, have since followed the Star Wars path, with two interconnected sequels being planned simultaneously after a smash-hit first installment. More recent hits, including The Lord of the Rings and the Swedish films based on Stieg Larsson's Millennium books, were planned as a trilogy from the beginning, but the effect is the same—if you want one story, you have to buy three tickets.

But unlike trilogies, quadrilogies tend to happen by chance: Audience demand for another installment is high enough that Hollywood executives shrug and give it to us. In fact, despite my best efforts, I haven't been able to find any four-film franchises in Hollywood history that were originally intended to be quadrilogies (the five Twilight films come closest, with the eight Harry Potter movies as their general model; The Hunger Games will reportedly be the first). Quadrilogies tend to be far more episodic, relying less on a continuous plot and more on a consistent group of characters or setting. Pirates of the Caribbean: On Stranger Tides, for example, stands alone much more coherently than the mythology-heavy third installment, At World's End.

The episodic nature of quadrilogies makes them particularly well-suited to children's films, which have an audience that demands much less consistency and continuity. But Hollywood was surprisingly slow to turn its biggest children's hits into theatrical franchises—opting to make low-cost, direct-to-video sequels for decades. There are no fewer than 12 sequels to 1988's The Land Before Time, a number rivaled only by the surprisingly sprawling Air Bud franchise. Disney routinely opted against making theatrical sequels to its most popular films; Aladdin was the top-grossing movie of 1992 by a considerable margin, but its two sequels—1994's The Return of Jafar and 1996's Aladdin and the King of Thieves—were direct-to-video affairs.

The direct-to-video model still exists, with cheapo sequels to underperformers like Open Season or Happily N'Ever After, but the market may be changing. Ice Age: Continental Drift 3D marks only the second time that the fourth film in a children's animated franchise has had a theatrical release (behind Shrek: Forever After)—and with a reported production of $100 million, Ice Age: Continental Drift 3D is the most expensive installment in franchise history. Other studios are close behind; movies like How to Train Your Dragon and Despicable Me have sequels on the horizon, and two of Pixar's last three films have been sequels—with a prequel, Monsters University, due next year.

If Ice Age: Continental Drift 3D and its cinematic peers are any indication, we're swiftly approaching the final wrinkle of the franchization trend: the breakdown of the wall between trilogies and quadrilogies, and the idea of a broadly-defined "franchise." Many of film's most iconic trilogies aren't even trilogies anymore. Star Wars became a hexalogy. The Hobbit will provide a prequel to the Lord of the Rings trilogy later this year. Live Free or Die Hard and Indiana Jones and the Crystal Skull turned their original trilogies into quadrilogies long after both series were presumed to have permanently ended. It's gotten to the point where director Christopher Nolan made headlines by insisting that there will be no further Batman films from him after this week's The Dark Knight Rises, the third in the series. "We want to finish our story ... rather than infinitely blowing up the balloon and expanding the story," he said in 2010. If he sticks to his word, he'll be bucking Hollywood convention: There may not always be a tale left to tell in a franchise—but as long as there's money left in the franchise, the movie industry will likely find a way.