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But animated films weren't always like this. Quick—name the voice behind Snow White inSnow White and the Seven Dwarfs. No luck? What aboutPinocchio? Or Cinderella? OrOne Hundred and One Dalmatians? Or even a film as recent as 1992's Beauty and the Beast? Hats off if you managed to come up with Paige O'Hara (Belle) and Robby Benson (Beast)—but you're in the great minority of filmgoers.

When did celebrities take over the world of voice acting? Less than 20 years ago, voice acting was almost exclusively the realm of voice actors—people specifically trained to provide voices for animated characters. As it turns out, the rise of the celebrity voice actor can be traced to a single film: Disney's 1992 breakout animated hit Aladdin. Though Aladdin boasted some of the world's most seasoned voice actors—including Frank Welker, whose astonishing range of characters include Scooby-Doo, Kermit the Frog, and Transformers' Megatron—there was one man who stood out from the rest of the cast: Robin Williams, who voiced the film's hyperactive Genie.

In many ways, it was the perfect pairing of actor and character, and Williams's manic energy made for a undeniably great Genie. But the casting decision came with a catch—it's also impossible to separate the Genie, as a character, from the public persona Robin Williams. Aladdin's Genie constantly breaks the fourth wall, winking at the audience and doing impressions, from Arnold Schwarzenegger to Jack Nicholson, that are just a little anachronistic for the film's ancient Arabian time period. Though the film was named after Aladdin (voiced, you almost certainly don't remember, by Scott Weinger), Williams's Genie is the character audiences responded to, and—more importantly to Disney—its most marketable character by far.

The celebrification of voicework can be traced through the films Disney released in the years after Aladdin, from The Lion King (Jonathan Taylor Thomas, Whoopi Goldberg, James Earl Jones) to Home on the Range (Roseanne Barr, Dame Judi Dench). But the trend has been most prevalent in the computer-animated films that have dominated family-friendly cinema since Pixar released Toy Story in 1995.

The marketability of a big-name celebrity voice actor gave way, perhaps inevitably, to an even more insidious trend: directly basing a character's appearance on the famous actor providing its voice. The examples range from the Jerry Seinfeld bee inBee Movie to the Tina Fey-esque reporter inMegamind, but the apex is Dreamworks' 2004 animated film Shark Tale, which features creepy human-fish hybrids of actors like Will Smith and Angelina Jolie. Pixar, ahead of the curve as always, has attempted to back away from relying on A-List actors, with terrific results; the studio's two best films in recent years (and, arguably, of all time) are Wall-E­—whose robotic leads can only speak variations of their names—and Up, which starred Ed Asner and newcomer Jordan Nagai.