Stop me when you’ve heard this one.

A boy leads a mundane existence throughout childhood, then during his early teens he learns a secret about his parents and discovers he possesses supernatural abilities. So the lad is whisked off to a hidden world where he will be educated and trained along with scores of other kids with similar powers, all the while fighting a mysterious villain.

No, this isn’t a synopsis of “Harry Potter and the Sorcerer’s Stone.” It’s the scenario for “Percy Jackson & the Olympians: The Lightning Thief.” Based on Rick Riordan’s young adult novel, this movie is what you get when you combine Harry Potter with “Clash of the Titans.”

The biggest difference between the two teenage heroes is that in “Percy Jackson & the Olympians,” the supernatural powers come from Greek mythology rather than magic.

The biggest surprise is how enjoyable the movie is, despite being so derivative.

The movie begins with Poseidon (Kevin McKidd) strolling out of the East River and onto a pier in Manhattan, in giant form. He morphs into human scale, then proceeds to the top of the Empire State Building, where he has a heated argument with Zeus (Sean Bean).

And immediately, this knock-off of better young-adult fiction begins to defy the odds and win us over. It’s just plain fun to watch Zeus and Poseidon having a tete-a-tete atop Manhattan’s signature landmark rather than on Mount Olympus.

Zeus informs Poseidon that someone has stolen his lightning bolt, and many of the gods suspect Poseidon’s half-human son is the thief.

Meanwhile in the human world, misfit teenager Percy Jackson (Logan Lerman) hates school and fights with the guy (Joe Pantoliano) his mom (Catherine Keener) lives with. Add to that a father who abandoned Percy and his mom when he was just a baby, and Percy is one thoroughly angst-ridden teen.

What sets Percy apart from all the other brooding teens is some strange abilities. He can hold his breath under water for seven minutes. He struggles with dyslexia — when reading English. He soon discovers he understands Greek, even though he has never studied it.

When Percy and his best friend Grover (Brandon T. Jackson) go on a class trip to the Metropolitan Museum of Art, secrets begin to be revealed. Grover and Mr. Brunner (Pierce Brosnan) save Percy when a substitute teacher turns into a fury and tries to kill him.
Mr. Brunner orders Grover — who is a satyr in disguise and Percy’s designated protector — and Percy’s mother to rush Percy to a remote woodland camp for demigods.

As you’ve guessed, Percy is the demigod son of Poseidon. It turns out there are many demigod kids, many of whom live and study at Hogwarts — I mean, in the demigod camp.

The only things missing from the demigod camp are Hagrid, wands and quirky teachers. Except there is one quirky teacher. Mr. Brunner is actually a centaur, so we get to watch Brosnan walk around with a horse’s back end.

“Percy Jackson” even shares a director with Harry Potter, Chris Columbus, who helmed the first two Potter installments.

After we reach the demigod camp, the story begins to race along and becomes a nice mix of action scenes and references to Greek mythology. Percy, Grover and their demigod friend Annabeth (Alexandra Daddario) encounter Medusa (Uma Thurman), Hades (Steve Coogan), Persephone (Rosario Dawson) and other mythological beings.

The action sequences and copious scary images make this PG movie appropriate for pre-teens and older, even though the scenes with Rosario Dawson playing seductive in a bustier alone make it borderline PG-13.

“The Lightning Thief” will almost certainly become a franchise, regardless of its shameless pilfering. It boasts an incredibly strong cast and flashes along with an earnest spirit and a playful use of Greek mythology. It may be second-rate, but it’s all in good fun.

Jeff Marker is a media studies professor at Gainesville State College.