You might have walked into the Emerald City. The art deco auditorium of Hammersmith’s Apollo is bathed in green light, the stage dressed with a curtain of ivy. But we’re meeting an ogre not a wizard and, this being Shrek, he’s in the outhouse taking a dump.

There’s plenty more toilet humour to come in this revival of Jeanine Tesori and David Lindsay-Abaire’s 2008 musical, based on the 2001 Oscar winner and William Steig’s book, now in London after a UK and Ireland tour. With booming narration, it is played at the volume of a pantomime and comes with panto’s random topical references (to Jude Bellingham and Baby Reindeer). There are some game performances – and Cherece Richards is on fire with a sensational singing voice as the Dragon – but the show becomes bogged down by its sludgy monotony and often unmemorable songs.

The best number, Story of My Life, with Pinocchio and other fairytale figures lamenting their lot, comes early on. Freak Flag, the same ensemble’s This Is Me-style anthem of empowerment, fails to raise the roof later in the evening. Shrek’s pal Donkey channels Otis Redding and advises his friend with a few bars of Try a Little Tenderness in the animated film; on stage, in a furry costume, Todrick Hall is more like Isaac Hayes as he dons shades while funkily imploring the ogre to open his heart to Princess Fiona. In the film, Monsieur Hood’s merry men veered from Riverdance to West Side Story rumble to old-school razzle-dazzle; the musical hits a high note with Fiona and the Pied Piper’s routine featuring a rodent chorus line and gives Lord Farquaad (James Gillan) some humorous prancing guards.

Farquaad, mocked in the film for being short, has been played in the past by an actor on his knees. That’s not the case here but the production has not resolved how to present the character, oddly fudging some sections. Fiona’s lyric about seeming “a bit bipolar”, meanwhile, is left uncut.

The musical adds a prologue, with seven-year-old Shrek sent off to fend for himself by his parents, linking his years of isolation to Fiona’s, banished in a tower since the same age. The sparks don’t fly as they should in their duet I Think I Got You Beat, and you never sense love in the air, but Antony Lawrence and Joanne Clifton do convey the pair’s goofy humour, with their burping battle a crowd-pleaser.

Co-directed by Samuel Holmes and choreographer Nick Winston, with projections by Nina Dunn and sets and costumes by Philip Witcomb, the show often feels flatly unadventurous, typified by its lacklustre bridge-crossing sequence. Onions and ogres have layers, we’re told, in a line from the film. This musical? Not really.