Which raises the obvious question: What on earth is going on? Why has Scooby-Doo—described by the New York Times film critic A. O. Scott in 2002 as “one of the cheapest, least original products of modern American juvenile culture”—outlasted not only such Hanna-Barbera brethren as The Flintstones and Yogi Bear, but also pretty much everything else on television? The Washington Post’s Hank Stuever once summed up the cartoon’s message as “Kids should meddle, dogs are sweet, life is groovy, and if something scares you, you should confront it.” But that hardly seems enough for half a century of on-air appeal.

The essential premise, for those not weaned on the show, is straightforward. A group of four teenagers—some of whom seem considerably older (more on this in a moment)—and a Great Dane, Scooby-Doo, drive around in a van called the Mystery Machine in search of, yes, mysteries. (The gang, like its later Hanna-Barbera cousin, Josie and the Pussycats, was originally conceived as a band that would play a musical number each episode.)

The mystery they find almost always appears at first to be paranormal—a vindictive ghost or ghoul, a rampaging dinosaur—but is ultimately revealed as an elaborate hoax involving disguises, holograms, hidden wires, phosphorescent paint, or some combination thereof. Each time the gang unmasks the genuine villain, typically male and on the older side, he utters some variation of “And I would’ve gotten away with it if not for you meddling kids.”

The Mystery Inc. members are Fred, the blond, broad-shouldered presumptive leader of the group (who wears, implausibly, an ascot); Daphne, the fashion-conscious redhead and semi-comical damsel in distress (a stereotype that the show subverted in its later iterations); Velma, the frumpishly sweatered and bespectacled brainiac; and Shaggy, the ever-famished slacker-coward defined by his prominent slouch and chin grizzle. Scooby himself—his name was inspired by Frank Sinatra’s “dooby dooby doo” scat in “Strangers in the Night”—is inseparable from Shaggy and in many ways indistinguishable: same appetite, same poltroonery, same plot functions. Essentially split aspects of the same character, the two are not id and superego, but something closer to id and more id. A typical story line involves Daphne getting kidnapped or otherwise endangered; Fred devising a Rube Goldberg–esque, and spectacularly unsuccessful, trap to ensnare the villain; and the case being wrapped up by a blend of Velma’s smarts and Shaggy/Scooby’s bumbling good luck.

The show owed its launch in part to complaints that Saturday-morning cartoons—including Hanna-Barbera’s Space Ghost—were becoming too violent. So the producers William Hanna and Joseph Barbera (along with the story writers Joe Ruby and Ken Spears, and the animator Iwao Takamoto) decided that their new show wouldn’t merely solve mysteries; it would demystify them altogether. As any parent knows, the surest way to comfort kids is to offer them an alternative explanation for the horrors that go bump in the night: It was the cat, or the wind, or the uncle who forgot where the guest room was. In the premiere of Scooby-Doo, “What a Night for a Knight,” the ambulatory suit of armor freaking everyone out is discovered to be Mr. Wickles, the seemingly hapless museum curator who is also (gasp!) a secret art smuggler. Case closed. Sleep tight.