‘Nightmare! I’ve got to tap-dance with four legs!’ Inside the new SpongeBob Musical

“Who lives in a pineapple under the sea?
Absorbent and yellow and porous is he!”

If these words don’t set your foot tapping, or prompt famished thoughts of Krabby Patties, then you may not be the target audience for a musical that brings to the stage the psychedelic deep-sea inhabitants of Bikini Bottom: namely, the irrepressibly chirpy SpongeBob SquarePants, his dopey best friend Patrick Star and the squirrel Sandy Cheeks, an inventor with martial arts moves.

The SpongeBob Musical, based on the Nickelodeon cartoon that first aired in 1999, opened on Broadway in 2017. Reviews of the trippy $20m production, in which the future of Bikini Bottom is threatened by a volcano, amounted to a series of approving variations on the theme of: “What were they smoking when they came up with this?” The New York Times even suggested theatre-goers might benefit from “some illegal inhalation”. The original cast included Stephanie Hsu, later Oscar-nominated for Everything Everywhere All at Once, and the earworm-heavy score featured new songs by bands such as the Flaming Lips, Aerosmith and Panic! at the Disco, who wrote the show’s air-punching anthem (Just a) Simple Sponge.

“What’s so good is that you don’t stay in one musical style for very long,” explains Tara Overfield Wilkinson, director of the new touring version, when I drop in on rehearsals. In one corner of the west London dance studio, the ex-Pop Idol star Gareth Gates is practising the steps he will perform as the whingeing Squidward in the big tap-dancing number. “I haven’t tapped in my life,” he says. “Plus I’ve got to wear an extra pair of legs, so it’s going to be a nightmare.” Over by the mirror, Lewis Cornay – SpongeBob himself – is working out the complicated handshakes he and Patrick (Irfan Damani) will exchange. “I didn’t watch the cartoon as a child,” admits the elfin 27-year-old. “But I love the album. It’s funny being at the gym and no one knows you’re listening to (Just a) Simple Sponge.”

On Broadway, the show nabbed six Drama Desk awards and earned 12 Tony nominations, winning one for set design. Yet still it closed nine months later without recouping its costs. One theory is that it never quite identified its audience. The casting of the new production covers several bases – the musical theatre crowd (Cornay starred in The Book of Mormon), pop devotees there to see Gates, and Ru Paul’s Drag Race fans showing up for Divina de Campo as the villain Plankton. Has the director considered who her show is for? “Of course. Children will love it but they aren’t the ones buying tickets, so it has to be enjoyable for the parents and grandparents. As with panto, there are jokes that will go over kids’ heads. It’s nice that it’s all very humanised: the cast aren’t hidden by masks.”

Cornay, for instance, will sport yellow hair, a yellow shirt decorated with bubbles, and a stunted red tie. Voices will go some way towards bringing the cartoon characters to life. “They’re not impersonations but you want the essence,” says Wilkinson. “We haven’t suddenly made SpongeBob Scouse.” The actor slips briefly into the character’s gleeful chirrup for my benefit, then grimaces. “I’ve got to find a way of doing that eight shows a week without getting nodules,” he says.

The cartoon’s busy-bee surrealism has been justly celebrated but its casual acceptance of difference also chimes with our times. “With today’s concerns about diversity and inclusion, it’s wonderful to have a sponge, a starfish and a squirrel be best friends,” says Wilkinson. The 22-year-old Chrissie Bhima, who plays Sandy Cheeks, detects some political commentary in the show. “If you strip away the underwater setting, there are some meaningful moments,” she says. “Sandy is a land mammal living in the sea. To be a Black person on stage, and for some of the characters to have pitchforks and to be saying, ‘Blame the squirrel’ – it’s like, ‘Whoa!’ Especially after Black Lives Matter.”

Cornay has come across some wild theories during his research. “I read one comparing Squidward to Hitler,” he says with a shudder. But he does see an environmental message in the show. “It very cleverly talks about climate justice, and the power of community, without being preachy,” he says. Wilkinson and her cast have also found some unexpected parallels. “There’s a scene where Mrs Mayor tells the whole town everything is fine, she’s got it all under control. We immediately groaned because it felt like Boris Johnson at the podium, so we’ve made a bit of a joke about that.”

Next on her to-do list is some prop buying: she’s off to order paddling pools and spatulas for the opening number. Even amid the wackiness of Bikini Bottom, though, it’s vital to stay grounded. “It’d be easy to be like, ‘Oh, you’re just playing a cartoon, you don’t have to think about it,’” says Cornay. “But actually, there’s nowhere to hide with this. You need to give it the same conviction you would bring to any part. Otherwise you’re running round on stage looking flustered.” Another grimace. “And no one wants that.”

• The SpongeBob Musical is at the Mayflower theatre, Southampton, 5 to 8 April, then touring.