This doesn’t usually happen: I’ve turned up to interview two people, and neither of them are here. Ed MacArthur, co-creator of String v Spitta, a hit comedy show about rival kids’ party hosts, has Covid, and is beaming into a Soho theatre meeting room via Zoom. Kiell Smith-Bynoe, his partner in crime, is wrapping up a 10-week shoot on series four of the sitcom Ghosts, and is running late. “I get the sense,” MacArthur says as we wait, “that Kiell was pretty elite.” We’re talking about their work in children’s entertainment. “He had his magic tricks and great costumes. Whereas I was just playing classical music and telling stories to babies.” That was back in the day, when MacArthur supported his fledgling performance career with “about 27 sidelines,” glorified childcare included. “It was usually just me and loads of au pairs who didn’t speak English. I found myself making jokes to a room of only children and people who didn’t understand what I was saying. Whereas Kiell was doing all the bells and whistles.” As if on cue, the Ghosts actor bustles in and says his hellos. Is it true, Kiell, that you were once the bells-and-whistles king of children’s entertainment? “I was getting kicked a lot,” he replies, flatly. “Let’s not forget that. I got kicked all the time.” String v Spitta launched at Soho theatre, London, just before Christmas, and was an instant hit – albeit after a long gestation period. MacArthur and Smith-Bynoe were introduced at the Edinburgh festival fringe in 2016, the latter pre-Ghosts and not long free of his side hustle with the kids’-party outfit Simply Smiley. Standout memories? “Bank of England governors day,” he recalls with a grimace, “when all the important people from the Bank of England are like, ‘do something with my kids!’ and then they get absolutely smashed.” When the duo discovered this shared history, they began plotting a comic two-hander about that under-explored world, one that drew on the lessons they learned while performing to infant audiences. “If you turn your back, their attention goes elsewhere,” says MacArthur. “So every moment has to be entertaining – and if not, why not? That’s quite a useful rule.” MacArthur and Smith-Bynoe are musicians, and soon they were cheerfully reworking children’s party songs for comic effect. “Which was cool,” says MacArthur, “because so many children’s songs are absolute bangers.” Characters emerged: Sylvester String, old-school kids’ entertainer and disciplinarian; and TikTok rapper Spitta, the new kid on the block, whose improvised grime stylings – not to mention the balloon animals (“I only remember how to do a dog,” says Smith-Bynoe, “or a giraffe, which is a dog with a long neck”) – the tots adore. As if channelling Sylvester String, MacArthur cites Peter Shaffer’s Amadeus as an influence. “I’m the posh Salieri establishment artist who takes the traditions of the art form incredibly seriously, and has great relationships with all these parents. Then in comes this absolute maverick who does not play by the rules, and disrupts everything.” Their December gigs (the run was curtailed by Omicron) told the story of the pair’s fractious relationship in flashback while they delivered their double-act to the offspring of Russian oligarchs – AKA, the audience. “When we realised we could treat an adult audience like children,” says MacArthur, “that was the big theatrical discovery.” Alongside the improvised rap battles, the repurposed Twinkle Twinkle Little Star and Heads, Shoulders, Knees and Toes, and the droll commentary on class rivalries in the capital, much of the considerable fun in String v Spitta is in reliving the children’s party experience as grownups. “Most of our audience and peers wouldn’t have been involved in a children’s party for 25 years,” says Smith-Bynoe. “It’s about nostalgia, and the excitement that this time around, we can do it with drink, be a bit naughty and shout back.” By popular demand, and assuming the pair ever get themselves back into the same room, the show returns next week for a short run. “We’ve got big plans for how we can make it step up,” says MacArthur. Smith-Bynoe raises an eyebrow. “Well, I’ve got big plans,” says MacArthur: “I just haven’t shared them with you yet.” One unavoidable tweak will be to the Russians-in-Kensington backdrop. “That world of the super-rich outdoing each other with the grandest children’s parties is going to feel way more red-hot than it did at Christmas.” “We’ve got two weeks to rewrite the whole show,” says Smith-Bynoe. “We’re thinking of writing a song called Londongrad Is Burning Down,” says MacArthur. Beyond that, the dream is the small screen: String v Spitta is already a few drafts into its TV treatment. “We’re really hoping we get to make it,” says Smith-Bynoe. “I adore doing the live show. It makes me laugh every night – seeing the responses from the audience, and the feeling of being kept on my feet. I’m having the time of my life doing it. But at the same time, I’d love to get some money for it, do you know what I mean?” String v Spitta is at Soho theatre, London, 6-16 April.