Hey, dog! How do you do the voodoo that you do so well?

Here’s the easiest way to comprehend the longevity of Scooby-Doo: Casey Kasem has been doing the voice of Shaggy (Norville Rogers, if you insist on his given name) for longer than he hosted his weekly Top 40 radio show. He started voicing Shaggy in 1969, the year before American Top 40 debuted, and he’s still got the part, on television in the WB’s Saturday-morning cartoon, What’s New Scooby-Doo?, and in the direct-to-video movies the franchise keeps churning out.

Though it’s hard to believe—and for animation purists, practically impossible to stomach—Scooby-Doo is the most enduringly popular cartoon in TV history. Starting with the original Scooby-Doo, Where Are You!, the show, in various permutations, was produced for 17 years (and, with its latest incarnation, it’s in production again), making it the longest-running network cartoon ever. Because of syndication, it’s never been off the air since it debuted, and it probably never will be. Now it’s expanding its empire: Scooby-Doo 2: Monsters Unleashed opens today in theaters nationwide, the second of what promise to be many live-action Scooby movies. In 2002, the live-action Scooby-Doo raked in $54.2 million on its opening weekend, on its way to a $153-million box office.

Acknowledging Scooby’s durability is easier than explaining it. Scooby-Doo wormed its way into the culture through years of drip-drip accretion. It’s the Cal Ripken of cartoons: Not the best, though certainly not the worst, it just shows up day after day after day, and you end up loving it for it.

For years, not even the show’s creators at Hanna-Barbera—the first TV animation studio and the inventors of “limited animation,” (that is, animation cheap enough for TV-size budgets)—realized the appeal of Scooby-Doo. Instead, The Flintstones, or even The Jetsons, was thought to be the studio’s flagship property. The 1989 50th anniversary TV special for Hanna-Barbera was dubbed “A Yabba Dabba Do Celebration.”

But Bedrock might as well be the, uh, Stone Age for today’s young audiences, while the gang at Scooby-Doo maintains its hypnotic appeal. The eponymous dog star’s Q rating tops Bugs Bunny’s among kids. The franchise’s direct-to-video titles consistently hit the best-seller lists. (And yes, in a nod to changing times, Scooby, Shaggy, and Fred do DVD commentary.) Kid-oriented Scooby-licensed video games have been popular since the mid-’90s. In 2000, Scooby-Doo won a mock presidential election held by the Cartoon Network, which still airs an hour-and-a-half of Scooby shows each weekday as part of its “Scooby Universe” package. Unlike the evening “Adult Swim” fare, the Cartoon Network’s daytime audience is dominated by tykes. One key to understanding Scooby is to realize it has never performed the double-ironic back flip that would make it an adult phenomenon. It has always appealed first to little kids.

One early hint of the show’s hold on children came in February 1971, when the BBC pulled Scooby-Doo, Where Are You! from the air, and 70 Scottish children staged a protest outside the Beeb’s Scotland headquarters. An employee recently told the Scottish Daily Record that the protest remains the biggest at that BBC location’s history. But beyond making comparisons to the Hardy Boys and Nancy Drew, or citing the general appeal of talking dogs, or noting that Daphne is as sexualized as a kiddie cartoon character gets, it’s difficult to say exactly why the show has had such a long-standing appeal. It’s not as if the show’s animator, Iwao Takamoto—his other creations include the Great Gazoo of The Flintstones and Grape Ape—is an unheralded genius, a mystery-genre Tex Avery or Walt Disney. “I never got it,” complained Mitchell Kriegman, the creator of Nickelodeon’s Clarissa Explains It All, to the Boston Globe a few years back. “It’s got kind of a slacker appeal, a no-resistance story line.” Animators and children’s TV creators around the world must see Scooby and ask themselves: Why can’t my crappy show become iconic?

Jim Millan, the writer-director of Scooby-Doo in StageFright—Live on Stage (yes, there was a touring theatrical production of Scooby-Doo) tried to engage in some bigthink about the show’s popularity during publicity interviews. “They like Scooby’s enthusiasm for life,” he theorized to the Baltimore Sun. “It represents a youthful, optimistic America, where you can solve a problem with good intentions.” To the Toronto Star, Millan compared Scooby-Doo to 19th-century European commedia dell’arte, with its stock characters and costumes. “Scooby and Shaggy love to eat,” Millan said. “But the delight is in seeing the permutations.” To Nashville’s Tennessean, Millan said of Scooby, “He symbolizes youth, in a way.”

TV snobs surely see Scooby’s ineffable charms as another brick in the wall of American decline, the latest example of how we’re all slouching toward Toon Town. As if our children should all be watching The Sopranos. Maybe Scooby’s appeal makes sense when you compare it to the rest of kids’ TV. The most ham-handed of children’s shows try to stuff a moral message down the audience’s throat. But the moral code of Scooby-Doo permeates the entire enterprise without you ever noticing it. The Washington Post’s Hank Stuever concisely elucidated the “Scooby worldview” when the first live-action movie came out: “Kids should meddle, dogs are sweet, life is groovy, and if something scares you, you should confront it.” What needs to be explained about that?