COLLISION of shapes: Penelope Square (Kirsty Marillier) testing the boundaries of Lily Polkadot (Gugu Dhlamini). Photograph by Ronel Hugo.

YOU KNOW THE shtick: an outsider wants to be part of the in group, but she’s rejected and hurt, laughed at and humiliated. She’s blatantly willing to do anything in her power to be loved, but fails. And then something happens and the world becomes a kinder place. Off-Broadway musical Polkadots debuted at this year’s RedFest at Red Hill school, and the children’s live show will run for another week, giving little people all over the city the courage to be.

Think of the Hans Christian Anderson chestnut, the Ugly Duckling, or works seen on local kids’ stages in the last little while, including Honk! and Freckleface Strawberry, and you will have a clear view of the trajectory of the tale. But this brightly coloured piece of delight is not about narrative nuances. It’s a luminously happy tale of unfairness and judgement based on appearances, peppered with lovely lessons, catchy songs and real value. And then, there’s the costumes, which are so fantastic that even if you hate every other aspect of the show, you will be utterly charmed at the geometric kaleidoscope unravelling here.

The suburb of Rockaway is populated by children who are square. Not in the pejorative sense, you understand, but quite literally: their surnames are all Square. Their clothing bears the mark, as does the water fountain from which they can drink. Even their hairdos comply. What happens when a young polkadot (Gugu Dhlamini) moves into the area? The world turns on its axis and lessons get learned.

Dhlamini reprises the role of Lily with complete focus and ownership. She takes on the whole stage with a sense of maturity that gives credence to her character. Her singing voice harmonises magnificently with that of Andrea Shine, in the role of the teacher, Mrs Square. The child who cannot accept the newcomer is Penelope Square (Kirsty Marillier), and she’s grumpy and loud and shrieky but ultimately lovable.

But it’s in the shrieky department that this work sometimes compromises itself. Remember, you’re talking big voices and big catchy tunes in a relatively small auditorium. The actors all have mics taped to their faces. And the sound sometimes reaches beyond enormity and you can feel your teeth rattle with its vibrations.

That said, with crisp and satisfying choreography, bold performances, which also feature Bonginkosi Jay Hlatshwayo as Sky Square, the boy who is willing to make his social borders flexible, Polkadots gives you the sense that you have stepped into a comic book, lock, stock and barrel. You’ve left all hold on reality at home, and the world’s a simpler place.

• Polkadots is based on the book by Melvin Tunstall III, features lyrics by Douglas Lyons and is directed by Shelley Adriaanzen. It features design input by Shelley Adriaanzen (choreography), Rowan Bakker (musical supervisor), Greg Borowsky (music), Matthew Counihan (lighting) and Sarah Roberts (production design) and is performed by Gugu Dhlamini, Bonginkosi Jay Hlatshwayo, Kirsty Marillier and Andrea Shine, in the Red Hill school auditorium in Morningside, until October 6. Book here .