TUTTI Frutti artistic director Wendy Harris did not know Erika Poole and Josie Cerise had worked together already when she cast them as the old lady and young girl in this spring's premiere of Monday's Child.

"I like to base my choices on what I see in the room, during the auditions, not on what I might know about people beforehand, and so I hadn't connected Erika and Josie," says Wendy.

They did not even audition together but the director nevertheless instinctively judged them to be the perfect for the roles of Woman and Girl in Brendan Murray's newly commissioned play for the Leeds children's theatre company. Such decision making is always a good sign of a director on form.

It turns out that Tutti Frutti debutantes Erika, from Stoke, and Josie, from Manchester, had appeared together in the 2012 television series Ha! Ha! Hairies on Cartoon Nito, the pre-school channel.

"I was Nana Ha! Ha! and Josie was...Mini Ha! Ha!. We had a dog called Chihua Ha! Ha! – and the car in the show was Fluffer Puffer Poop," says Erika.

"But when we then auditioned for Monday's Child, we did it separately and we both thought we hadn't got the parts."

Josie had sent a text to Erika expressing that thought, but how wrong they both were. Wendy picked them both. "The weird thing would have been if one of us had got a role and the other hadn't!" saysJosie.

"But that's the nature of the game," says Wendy. "Though can i just say they're brilliant together in the show."

Monday's Child explores the relationship an old lady and a little girl as they share the delights and surprises of their respective stage of life, loving to sing and dance and dress up and often being oblivious of the challenges the real world throws at them. The idea for the play came from Wendy, whose mother-in-law has Alzheimer’s, and she asked regular associate Brendan Murray to write a play examining the themes of memory and discovery .

To research the project, Wendy and Brendan met with Dr Chris Bird, lecturer in psychology at the University of Sussex, and Dr Dennis Chan, senior lecturer in neurology at Brighton and Sussex Medical School, last November to discuss the neurological research behind memory loss and dementia.

"In the play, Brendan writes about the bond between an elderly lady, who is losing her memory, and a girl who's developing her memory box and filling it with stories, so it's a beautiful, intergenerational piece where we the young and the old come together and we see the young in the old and the old in the young," says Wendy.

Erika has drawn on her own experiences for her role. "Between acting jobs, I've been doing care jobs in London, working with elderly people in their own homes," she says. "They can be very quirky in what they remember, specific to their own lives, and it can be interesting trying to access the story of who they are."

Similarly, Josie has drawn on her relationship with her cousin Sophie's daughter Phoebe. "I play with her and read her stories, and for this play, I just pretend I'm Phoebe and think 'what would Phoebe be thinking?'."

Erika and Josie are enjoying working together again. "The fact thet we bonded through the TV show has really helped," says Josie. "Doing Ha! Ha! Hairies was very intense as we filmed 52 episodes in eight week, which can make or break a friendship – and it made ours.

"So I was thrilled that Erika got her role in this play because I knew it would be a fun experience both on stage and off it."

Summing up the play, Josie says: "For me, it's about age not being an issue in any way, and it doesn't matter how old or young you are; young people can help old people and old people can help young people and that's a great message, because when I was young I maybe didn't fully appreciate that two-way relationship, but now I'm older, I do."

Erika agrees. "It's about the two far ends of the journey in life, if you like, but I also think it's about the importance of play. To stay playful throughout your life is a very positive thing, but I think we tend to lose that as we grow older."

Wendy hopes the play will inspire the young and the older alike. "It would be great if grandparents came with their grandchildren," she says. "It's a gorgeous piece for families and it's good for schools too."

Should you be wondering if Erika and Josie will be teaming up again, the answer is yes, albeit they will appear in different episodes of Grandpa In My Pocket on CBeebies. "I play Wanda Whoops, Mr Whoops's sister, who runs the toyshop," says Erika, "And I play Millie and Mollie Muddleton," says Josie. "They get muddled up of course."

Tutti Frutti and York Theatre Royal present Monday's Child on tour until June 15. The play is suitable for children aged three to seven and their families.

Dates include York Theatre Royal Studio, Tuesday, 1.30pm; Wednesday to Saturday, 11am and 1.30pm; June 10, 11am and 1.30pm, at Little Feet Festival of Children's Theatre. Also Howard Assembly Room, Opera North, Leeds Grand Theatre, May 23 and 24, 11am. Box office: York, 01904 623568 or yorktheatreroyal.co.uk; Leeds, 0113 243 9999 or operanorth.co.uk/howard-assembly-room