Perhaps, if you don’t have a child in primary school, you will be blissfully unaware of Dog Man, Dav Pilkey’s series of graphic novels about a cop who – after a terrible injury – has his dog’s head sewn on to his own body, thereby creating a crime-fighting canine/human crossbreed. But if you’ve been swept up by the phenomenon – and Dog Man is a phenomenon, selling more than 70m copies in the decade since the first book was published – then you will know that this mutt has some serious star power: there’s a Dog Man film, video game, board game … and now a musical, arriving in the UK after off-Broadway success.

The Dog Man books are chaotic, hilarious and full of pathos, but writer/lyricist Kevin Del Aguila and composer Brad Alexander’s show leans largely on the former. There’s slapstick humour and jokes about butt-sniffing. When Dog Man is asked how his day is going, he replies: “Ruff!” It’s aimed at the younger end of Pilkey’s readership, which is confusing as there are also Dickens references.

The plot – based on several early Dog Man books in the 14-strong series – is actually a musical within a musical: George and Harold, the fictional writers of the Dog Man comics, have decided to put on a musical to prove to their teacher how easy that would be. Because they’re throwing it all together using whatever they can find in their cupboard, Timothy R Mackabee’s set is charmingly DIY – skyscrapers are made from cardboard and gaffer tape, characters shapeshift across soft toy/glove puppet/human actor form.

Our hero hound (Renan Teodoro) is pitted against Petey (Sam Kipling), the villainous cat, and Flippy (Vanessa Dumatey), a psychokinetic butterflyfish who has gained super-powers from eating “brain dust”. But there’s a twist! To help achieve his evil aims, Petey clones himself, expecting a similarly twisted replica to emerge – instead he mistakenly creates Li’l Petey (Rebecca-Jo Roberts), a super-cute and naive kid who insists on calling Petey “papa” (cue much “I’m NOT your papa!!”).

Li’l Petey is the books’ emotional core and no doubt parents will relate to the idea of suddenly having a mini-me in their world who annoyingly doesn’t behave as instructed. But as the energetic cast dance, sing and bark their way around the set like CBeebies presenters after three pints of Skittles, these more moving moments get buried in the production, directed and choreographed by Jen Wineman. There’s also a slight disconnect in seeing people act out these roles – would children not get more excited at seeing Pilkey’s cutesy characters come to life with big furry heads rather than, say, an orange beanie?

Translating a graphic novel into a musical was always going to throw up such hurdles. At one point the hyperactive George and Harold, played by Ricardo Mendes and Peter Lavery, bring a board onstage to try to replicate the “animated” flip-o-ramas from the series. “This isn’t working the way it does in the comics!” they complain. It’s a joke, but still – perhaps musicals aren’t quite as easy to pull off as George and Harold thought.