Crackers review – have yourself a merry ratty Christmas

In children’s theatre, little ideas can make a big impression. Take the opening announcement at the Polka, spoken by and directed at kids: “Please ask your grownups to be quiet!” It means my daughter Hilda, nine, is snorting with laughter before Crackers even begins. That’s also because its rodent star, Napoleon, is popping out of the cupboards and corners of Liz Cooke’s ramshackle kitchen set as we take our seats.

Amid the traditional blizzard of familiar pantos here’s an original new “festive farce” for children aged five-12, written by Charles Way. The Crackers – mum Sue, son Joe and daughter Maia – run a pet shop that’s losing customers faster than an akita sheds hair. Mum’s putting the house and shop on the market but Joe has a plan to save them. If only he could work out where great-grandma Cath’s beloved first husband stashed his diamonds during the second world war.

As soon as that mystery is introduced, Hilda is sleuthing in the seat beside me. “Maybe the rat has them,” she whispers, beadily eyeing the cheeky puppet designed by Michael Fowkes.

We wondered if the show might have a menagerie of puppet pets to admire but there’s barely any mention of other animals which seems a missed opportunity. Way’s script develops the nice idea that Mum (Amy Loughton) has worked with pets for so long she’s started imitating them in times of heightened emotions. Mind you, would the shop really be selling some of the animals she mimics?

Hilda is quick to recognise some classic annoying sister traits in Maia (Sera Mustafa) who hogs the bathroom, commandeers the cereal box and is always squabbling with Joe (Andy Umerah), mostly about the goalkeeper jersey he wears like a second skin. The bond between the pair is recognisable, just like the hustle and bustle of the Christmas Eve setting, as great-grandma Cath (Erika Poole) comes to stay and Mum’s new fella Mike (a multi-roling Phil Yarrow) lends a hand. Poor Mike endures most of the wallops required by farce: “Good acting!” enthuses Hilda as Yarrow slams to the floor to show Mike fainting. But the physical comedy in Nicky Allpress’s production doesn’t always reach giddy heights and the essence of credible logic to ridiculous circumstances – so vital to farce – is sometimes missing.

Still, it’s fun for a young audience to see the set dismantled and characters disappearing headfirst beneath the floorboards. There are some priceless one-liners – Napoleon is discovered paddling in the toilet like he’s on holiday in Spain – and the merry interaction with the audience includes cracker jokes and karaoke (Hilda is delighted to recognise Christmas songs from her school’s concert).

It blooms into a touching account of love whether it’s between wartime sweethearts, bickering siblings or one boy and his cranky rat. If it’s also baggy and unravels a bit, like a favourite festive jumper, then no great matter: “I really enjoyed that!” beams Hilda.

• At Polka theatre, London, until 15 January.