Justice Smith, left, Pikachu, voiced by Ryan Reynolds, and Kathryn Newton appear in a scene from “Pokemon Detective Pikachu.”

It’s got an adorable hero from an iconic media brand who is voiced by a proven box office master at snark. But, somehow, “Pokemon Detective Pikachu” never really gets arresting.

A neutered Ryan Reynolds tries hard but can’t make this live action-meets-animated movie gel. It’s plodding and listless and really not funny or smart enough. Turns out, you can’t copy “Deadpool” tricks for the PG set.

“Pokemon Detective Pikachu “ borrows lightly from film noir crime dramas to create a mystery in a world where humans and Pokemon coexist. A young man called Tim Goodman (the terrific Justice Smith) joins with Pikachu (Reynolds’ voice) to search for what happened to the man’s father, a missing detective. The movie’s best moments are those between the scenes, where the Japan-born creatures thrillingly share the same urban space as humans.

Smith is very appealing as a son coming to grips with the loss of his estranged father, but Reynolds, as a cute coffee-guzzling detective with a Sherlock Holmes’ deerstalker cap, ping-pongs from heartfelt to caustic uneasily and tries to mimic his best-known, fourth-wall breaking “Deadpool” movie character (“That’s a twist. Very twisty,” he says of one plot point.) It’s the most mismatched buddy flick since Will Smith teamed up with an Orc for “Bright.”

The film starts slowly, builds to a sort of plateau and then ends with the final third consisting of nonstop action sequences and an underwhelming conclusion. Ken Watanabe is underused as a police chief. Equally inexplicably, Suki Waterhouse gets credit for a role in which she never speaks and lasts about 15 seconds on-screen.

Speaking of speaking, you’re probably wondering why there’s any dialogue between the adorable pocket monsters and humans since Pokemon traditionally only just say their own names. Enter five screenwriters — Rob Letterman, Dan Hernandez, Benji Samit, Derek Connolly and Nicole Perlman. Their solution is a weird gas that makes everyone crazy but somehow allows Tim to communicate with Pikachu. Sure, gas.

The pair are joined by a junior reporter — really an unpaid intern tasked with writing listicles, played by a winning Kathryn Newton — who helps them get to the bottom of the mystery using shoe leather and guile. (This is a film that celebrates the media in a big way — there are newspaper clippings, honorable TV reporting and a respected giant cable network. “It’s not news if it can’t be verified,” says one character. Take that, fake news people.)

But it’s all a bit of a muddle. We meet some cool Pokemon — Charizard, Psyduck, Snubbull, Ditto, Magikarp, Cubone and Mewtwo — mixed in with a climate change joke and an attempt to burn a miming Pokemon with mimed gasoline. It’s a film that explores daddy issues and also riffs off “Silence of the Lambs” (“Are you gonna make me into a lampshade?” Pikachu asks his human minder). Some of it is very scary for younger kids; most of it is incomprehensible to adults.

Then there’s Rita Ora playing a research scientist. We’re not sure why that is but she also teams up with Kygo to supply the film’s signature song “Carry On” — a bland, lazy, derivative club banger. It’s perfect for this flat film.

Live-action feature film adaptations of video games have proved a dicey proposition in the past. For every “Mortal Kombat” there’s a “Prince of Persia.” This one just feels like a venal money grab from a mega corporation. You’ve played Pokemon Go, right? Call this one Pokemon Don’t Go.