Originally praised for thumbing its nose at the saccharine Disney tradition, the “Shrek” series today offers little to differentiate itself from the mouse-eared behemoth in terms of producing business models rather than children’s cartoons. It ain’t easy being green, but making green sure sweetens the deal. And in the case of the latest sequel, “Shrek the Third,” success, or maybe the pressure to succeed, stifles the free-spirited, rambunctious fun that once made Shrek and friends so widely appealing.

Franchises tend not to grow old gracefully, and the creators of “Shrek the Third” have obviously chosen to spread the burden with even more of an ensemble, hit-ormiss approach than they used in the last installment. A much subdued Shrek (Mike Myers) and curtailed Donkey (Eddie Murphy) are no match for the clever peanut gallery of fairy-tale refugees, ridiculous royalty, and the invaluable extra sidekick introduced in “Shrek 2,” Puss in Boots (Antonio Banderas).

Shrek, happily wedded to fellow nonstandard beauty Fiona (Cameron Diaz), looks and acts like a tired dad. When Fiona’s father, the King of Far Far Away (John Cleese), dies, royal succession falls to the couple, who are none too excited. Shrek’s reluctant quest this go-round is to track down the other remaining heir and spare himself the burden of the throne.

In the series’ continued ransacking of the classics, Arthur (Justin Timberlake), a picked-on twerp still in high school, turns out to be the kingdom’s unlikely inheritor. After fetching “Artie” and weathering a shipwreck, Shrek, accompanied by Donkey and Puss in Boots, enlists the aid of Merlin (Eric Idle), who’s become a self-help addict and hermit since suffering a nervous breakdown.

Back to represent the side of “not good” is Prince Charming (Rupert Everett), who in “Shrek 2” led a failed conspiracy to take the throne. Now a frustrated actor, he marshals a crack squad of marginalized fairytale villains and has-beens to make another run for power. Meanwhile, Fiona, contentedly pregnant (with who knows what), stays at the castle with other princesses to fret and get attacked by Charming, at least until the finale arrives with its appointed hour of clichéd “Charlie’s Angels”- style girl power.

“Shrek the Third” starts and ends strong, but in between it feels like an assembly line of gags and romper-room-volume song cues, apportioned out as if for easy yeaor-nay evaluation: shot, gag, new shot, gag. This is partly because of the lack of a strong personality at front and center. A bland father-to-be who seems to have forgotten to offend in good fun, a certain ogre seems to have jumped the Shrek.

How far can you go with a children’s cartoon in which parents can identify with the hero more than their kids? Typical of the boomer ogre’s backslide, a fireplace scene with the headstrong Artie starts out with a mocking, “That’s What Friends Are For” cue, but proceeds anyway to a squishy father-sonstyle pep talk. Imminent fatherhood may mean a bit of growing up and toning down, but it’s like wanting to see Bugs Bunny after he went respectable, switched to beta-carotene supplements, and quietly retired to a gated warren.

Thank the Gingerbread Man and Pinocchio, bit players besieged back at the castle, for their absurd comic relief, and in more than one sense. Their one-liners represent the rare comedy in the movie that doesn’t follow the grating formula of medievalizing current pop culture. Spanning the store-name gags (“Versarchery”) rehashed from the previous sequel, Artie’s whatevering classmates, and even Robert Bly “Iron John” references from Merlin, it’s one long cavalcade of self-flattering, referential narcissism.

Some of it is funny (though rarely more than one-note), but the film entirely bungles the ability of cartoons to transport you to a world of wonder. “Shrek the Third,” of course, is neither the first nor the last animated juggernaut to reflect contemporary culture back at us for the weakest of recognition comedy, but every new example of this habit of impoverished imagination is still dispiriting. It’s matched by a pedestrian visual style most interested in how animation can mimic camera movements and achieve ever-higher levels of rubbery-looking computer-aided detail.

All of which might be more excusable if Shrek’s particular brand of twisted tale even made sense anymore. Originally, the story of a physically unappealing ogre with a heart of gold who saves the day was meant to embolden outcasts everywhere, but the message has changed a bit: “Don’t worry if people make fun of you for being different — because you’ll turn out like them in the end.” That’s less a hymn to American individuality than a smug heads-up to an awkward adolescent. Gentility triumphs, and somewhere a real ogre is puking.

But fairy tales have always had their structural problems. Artie, wary of responsibility, is asked to believe in himself, but as with other royals manqués before him, it doesn’t hurt to be born to inherit a throne when you do get around to fulfilling your potential.

With “Shrek the Third,” the series begins to face its own problems of unfulfilled potential. Shrek and company are fairly amusing, and the one-liners once in a while even sly, but the formula feels strained and perfunctory without a foundation of inspired movie-making. Even from the newest of fairy tales, audiences should be able to expect magic rather than commotion, and genuine meaning rather than capital-M messages.