Given that Pokémon is the highest-grossing media franchise of all time – and especially in the aftermath of 2016’s bout of collective madness that was Pokémon Go – it should come as no surprise that the beloved video game / trading card series has received the live-action movie treatment. What is surprising is that that movie is Detective Pikachu, a neo-noir shot on 35mm in which everyone’s favourite oversized yellow rodent is a deerstalker-wearing, coffee-addicted officer of the law voiced by Ryan Reynolds.

Courtesy of Warner Bros.

Things get off to a worryingly bland start. We’re introduced to blank-slate protagonist Tim Goodman (Justice Smith), a young insurance salesman who discovers at the film’s outset that his estranged father, Harry, has died in a suspicious car accident. Harry was a police officer in Ryme City, a neon-lit metropolis reminiscent of Blade Runner (but obviously recognisable as East London) where humans and a melange of adorable critters known as Pokémon live together in harmony.

Things significantly pick up with the introduction of a certain Mr. Detective Pikachu, who shows up in the apartment of Tim’s father. Normally, humans are unable to communicate with Pokémon, instead hearing cutesy variations of the name of the creature in question. However, through a plot contrivance not worth going into, Tim is able to perfectly understand Pikachu, who turns out to have been Harry Goodman’s partner (and also his pet-slave; don’t think about it too much) and who is suffering from severe amnesia. Tim and his furry little pal resolve to crack the case of what happened to Harry and to Pikachu’s memory, and soon find themselves embroiled in a major conspiracy.

For a while, the series of wacky misadventures brought about by the investigation is exceptionally fun. This is largely owing to Reynolds, who effortlessly transfers the comic delivery that made Deadpool so great onto Pikachu. The film saves its best jokes for him – including a great gag about climate change – but it’s genuinely funny throughout; as in a hilarious interrogation scene with a Mr. Mime, a Pokémon that believes in the invisible objects it insists on miming.

Courtesy of Warner Bros.

Wonderful too is Kathryn Newton in the role of enthusiastic journalist (actually clickbait blogger) Lucy Stevens. Newton’s charisma, put to great use in last year’s Blockers, manages to surpass her character’s predicable function as love-interest. The film is nearly stolen by her companion Psyduck, a large duck-like Pokémon with crippling nervousness who will literally explode if they get too stressed out. Relatable, man.

What Detective Pikachu gets most right is what kind of film it wants to be. Of course it is in essence a feature-length advert for the Pokémon franchise, but it never feels like a cash-grab. The film doesn’t take itself too seriously, without succumbing to the lazily cynical tone of recent kids-movie abominations like The Emoji Movie or Peter Rabbit. It goes easy on the nostalgia, leaving easter eggs largely to the background, and – miraculously – there isn’t really any sequel-baiting to speak of.

It’s a real shame, then, that the film begins to completely fall apart around the hour mark. The twisty plot loses momentum, and then overcompensates by piling on flashy (read: messy) effects work. There’s more weirdness in the final act, but it’s much less welcome than earlier in the film. Bill Nighy shows up. Pikachu does insufficient detecting. Rita Ora gets an awful cameo as Professor Exposition.

Courtesy of Warner Bros.

Ultimately, it’s through a surrender to lazy blockbuster tropes that Detective Pikachu fails to live up to the pure nuttiness promised by its premise. (Who would have expected it from the director of such acclaimed films as Shark Tale, Monsters vs Aliens and that Jack Black version of Gulliver’s Travels?) Still, Reynolds and Newton manage to keep the film afloat, and Psyduck alone is worth the price of admission.

Pokémon Detective Pikachu is out now, distributed by Warner Bros. Pictures