After 38 attempts at adapting TV for the big screen, there are rules for what makes a dud and what makes a hit.

Columbia Pictures

TV junkies: get ready to feel déjà vu all over again. This weekend's buddy cop comedy, 21 Jump Street—which traces its origins to Johnny Depp's star-making series of the same name—is just the latest in a long line of TV-to film adaptations to hit movie theaters. The TV-to-film subgenre has seen more lows than highs over the past two decades (remember I Spy? Didn't think so), and 21 Jump Street is already one of its more acclaimed offerings. According to Metacritic's current numbers, 21 Jump Street is the second-most acclaimed movie adapted from a TV show ever—behind only 1993's The Fugitive.

It's a hopeful sign that Hollywood might finally be starting to crack the TV-to-film subgenre. The massive boom in TV-based film adaptations shows an intriguing shift in Hollywood's attitude toward the smaller screen: TV used to be the film industry's whiny kid brother, clamoring for attention from its older, flashier sibling. But times have changed. Major actors are no longer stigmatized for taking small-screen roles, and many critics have begun to argue that the best of television has surpassed the best of film. Hollywood, ever-vigilant for a bigger cut of the box-office, has spent the past two decades mining the small screen for potential big-screen blockbusters—and the results haven't always been pretty.

Why has Hollywood turned to classic television for ideas 38 separate times over the past 20 years? For the same reason that it's turned to teen lit, comic books, fairy tales, and board games: It works. Two of the biggest contemporary film franchises—Transformers and Mission: Impossible—are rooted in television series that had been off the air for decades. As production costs continue to increase, Hollywood can't risk losing money on a big-budget movie with untested appeal, and Hollywood figures that a name like Land of the Lost might trigger some small point of recognition in the back of your brain, making you more likely to take a chance on a movie ticket (hey, I didn't say it always works).

The sheer number of TV-to-film adaptations offers a terrific opportunity to analyze the best and worst of the subgenre—and to discuss how Hollywood can turn to the small screen to make great films (and huge grosses) for years to come:

Twist the show's premise.

The trickiest part of adapting a TV show for film is turning something that's designed to go on forever into a conventional, three-act film. The movies that merely mount a no-frills replica of a small-screen premise—including My Favorite Martian and The Adventures of Rocky and Bullwinkle—have been failures. The best of the genre find a unique spin on an old premise. 21 Jump Street follows in the footsteps of The Brady Bunch Movie and Starsky and Hutch by openly mocking its TV predecessor—lampshading the ridiculous "young-looking cop infiltrates a high school" premise by casting Channing Tatum as one of the film's two undercover cops, and having the characters constantly ask if he's actually a teenager. (Of course, this can also be taken too far: See the film version of Bewitched, which built its bizarre, high-concept story around a real witch taking the role of Samantha in a remake of the TV series Bewitched.)

Pay homage to the original series...

Nothing makes fans angrier than a film that deviates from what they loved about the original. It's a lesson that G.I. Joe: The Rise of Cobra learned at its own peril when it cast Joseph Gordon-Levitt as the villainous Cobra Commander—without the character's trademark mask (the film's upcoming sequel offers a more conventional take on the character). Recognizing and including the iconic aspects of a franchise—the theme song of Mission: Impossible, the General Lee of The Dukes of Hazzard, or the shoe phone of Get Smart—is the key to keeping fans happy. And if you really want to go above and beyond, get the original cast involved. The Transformers franchise got a major PR boost when it recast legendary voice actor Peter Cullen as the heroic Optimus Prime—winning over skeptical fans in the process—and 21 Jump Street earns similar goodwill by including a winking cameo from a former cast member.

...But don't be too faithful.

Just as some things can't be changed, some things must be. Many TV-to-film adaptations have been derailed by their unwillingness to deviate too far from their original source material. 2009's The Last Airbender, which was based on a highly acclaimed animated series, was a muddled mess of nonsensical exposition on film, cramming a TV season's worth of storylines into a single movie. The Smurfs' insistence on including what felt like hundreds of the series' innumerable one-note critters was similarly irritating. Fidelity is admirable, but you're making a movie, not a TV series - so cut the seasons of fat away and get to the meat of your story.

Want critical praise? Adapt an action series.

The only four films on the TV-to-film list to earn "generally favorable" reviews—The Fugitive, Miami Vice, Transformers, and 21 Jump Street—each belong to the action or action-comedy genres. Other comparable films, including Mission: Impossible, Starsky and Hutch, and Get Smart, scored relatively well with critics—and significantly higher than any conventional comedies on the list. As a rule of thumb, action that played well on TV will play even better in theaters. There's higher stakes for the characters, more money for action set pieces, and a much bigger screen to show off all the action.

Want money? Adapt a cartoon.

Critics tend to turn their noses up at cartoon-to-film adaptations—the all-time highest-rated is George of the Jungle, which earned a middling 53/100 on Metacritic—but audiences flock to them in droves. Recent, critically reviled adaptations like Alvin and the Chipmunks and The Smurfs have overcome near-universal pans by combining broad appeal aimed at children with nostalgia aimed at their parents. As long as there are cartoons left to adapt—and bored children to entertain for an hour and a half—we can dread more sequels (or Squeakquels) in the future.

Hollywood will undoubtedly continue to search the annals of TV history for the next big potential blockbuster (in fact, it already has: Tim Burton's Dark Shadows, based on the gothic soap opera of the same name, hits theaters two months from now). In a subgenre littered with failed attempts, 21 Jump Street seems to have learned well from the successes and failures of its cinematic predecessors. All signs indicate that the movie will ride its critical raves to a strong box office finish—and a spot among the most successful TV-to-film adaptations of all time.

We want to hear what you think about this article. Submit a letter to the editor or write to