Something like “The Princess Bride” by way of Terry Gilliam, with some “Witches of Eastwick” thrown in like an eye of newt for good measure, the indefatigably fanciful “Stardust” is a fairy-tale mega-mix. At a little more than two hours, this adaptation of Neil Gaiman’s 1997 DC fantasy comic book series (illustrated by Charles Vess) and subsequent best-selling British novella, is overstuffed and a little too much of way too many things: romantic comedy, old-fashioned bildungsroman, musical theater spoof, computer-animated zap-fest, racy Victorian costume epic, and character-building parable.

Yet, since the story is propelled by a literally blinding optimism and a contemporary sophistication that subverts its Renaissance Faire flourish, it’s awfully hard to deny. Of course, die-hard fans of Mr. Gaiman’s original texts may disagree. Director Matthew Vaughn’s take is splashy and special-effects driven, with an extraordinary emphasis on galloping chase scenes interrupted by bouts of spell-casting, swordplay, and self-consciously corny humor.

But if the film holds together at all, it’s because the basic plot could just as easily serve an 1980s teenage-flick auteur like John Hughes.

Tristran (Charlie Cox), a prototypical callow youth who lives in the village of Wall, wants to prove his love to Victoria, the most beautiful girl in town (and aptly embodied by Sienna Miller, completing her “shallow sexpot” trilogy with “Factory Girl” and “Interview”). This lissome blond flake is no princess. She toys with Tristran’s affection and laughs when her studliest suitor bests him at swordplay. But when a falling star catches their eyes one night, Tristran pledges to find the stellar prize and give it to Victoria in exchange for her hand in marriage.

But of course, not everything is what it seems, or else there would be no movie. Tristran is no mere wannabe. He’s the secret heir to the kingdom of Stormhold, which lies in the Faerie realm just beyond a mysterious stone wall that gives his village its name, and is guarded by a hunched-over 92-year-old man who wields a fierce walking cane. As the audience already knows by this point, Tristran’s own father breached the wall in his youth and spent a wild afternoon with the lusty slave of a witch — a slave who turns out to be the lost daughter of the king (Peter O’Toole, grandly faded), whose seven sons have been steadily killing one another off in competition for the throne. It is the king’s death that kicks the narrative into gear, somehow triggering the descent of the star, which crash lands in the form of Claire Danes, now wearing the jeweled pendant — the Ruby of Stormhold — of the dead king.

Got all that? Well, rather than go on (and on), let’s cut to the chase: Tristran discovers the star, and incongruously insists on dragging her to his beloved. Luckily, destiny gets in the way, and soon the pair — squabbling like a couple of star-crossed (sorry) lovers in a 1930s screwball comedy — find themselves in peril.

Lamia (Michelle Pfeiffer), one of a twisted triad of witch sisters, is on the hunt. As it happens, only the radiance of a fallen star can restore her decomposing flesh and receding powers, though there is that problem of keeping the carnal being distracted while she carves out her heart and eats it. Secundus (Rupert Everett), the greediest of the king’s surviving sons, also aims to seize the ruby to claim his title — attended by a spectral Greek chorus of his gruesomely butchered and poisoned siblings.

Along the way, amid breathtaking vistas filmed on the Isle of Skye and in Iceland’s craggy outlands, farmhands are turned into goats, Ms. Pfeiffer becomes briefly gorgeous only to experience shocking physical erosion every time she casts a spell, and Ms. Danes’s so-called star, who goes by the name Yvaine, finds she really likes Tristran, even though he is ridiculously obsessed with this clueless Victoria chick. Robert De Niro appears as Captain Shakespeare, hamming it up as a lightning pirate who keeps a secret from his salty crew — underlining the film’s theme about the unreliability of appearances — while tilting the tone toward Monty Python. And then, but of course! The Brit of the moment, Ricky Gervais, takes a cameo as a motor-mouthed black marketer, the kind of character who usually turns up as comic relief on the various “Star Trek” franchises.

As much Cracker Jack box as enchanted saga, “Stardust” revels in the Rube Goldberg mechanisms of imaginary hermetic knowledge, while sweetly giving the softhearted romance fans what they came for: a supernatural love story. To say that it has the throwaway zest of one of those all-star Shakespeare in the Park productions is not meant as faint praise, even if its screenplay could have used a magic editing wand.