Bluey fan sites can be quite odd places. In normal times, adult enthusiasts of the wildly successful children’s cartoon post pictures of prime merchandise – like Bluey-themed silky bra and short sets or plush dog-shaped armchairs – and start conversations about which cheery canine character they most resemble.

But these are not normal times. This week Disney announced it would release the first full-length feature film based on the show, which features the eponymous anthropomorphic puppy and her family of Australian heelers, sparking widespread jubilation. The excited chatter was soon tempered with concern as the show’s creator, Joe Brumm, revealed in a blogpost that while he would write and direct the film, he would be stepping away from writing the TV series.

“Bluey has completely changed my life. It’s been an immensely satisfying thing to be a part of, more than I can really put into words,” he wrote. “To walk away from it while it’s at such a height will seem crazy to some but, for now, I am finding it difficult to reach back genuinely into that four- to six-year-old world and write authentically.”

Reaction among some fans of the show – which has delighted a legion of children and their parents since it was first broadcast on Australia’s ABC Kids in 2018 – verged on the histrionic. Brumm has insisted that his decision does not signal the end of the TV show, but some fans are unconvinced.

“What we know from history is that when the creator of a show stops working in it, the show then loses its essence and dies,” wrote a contributor on the “Adult Bluey Fans” group – which has 638,000 members. “So, enjoy Bluey while you can.”

Disney, which will release Bluey: The Movie globally in 2027, will hope the fans’ pessimism can be assuaged as it hitches its sizeable wagon to the cultural and commercial juggernaut. Produced by the Brisbane-based Ludo Studio in collaboration with BBC Studios – the commercial arm of the BBC, which cited the show as a significant driver of its growth in its most recent annual report – Bluey produces viewing figures that would make the most hardened TV executive weep for joy.

Crowned the most-watched series for preschoolers and kids in the US and Australia this year, it is CBeebies’ No 1 show in the UK and has 5.7bn views on the official Bluey YouTube channel.

But Bluey is no longer simply a TV show. This week Disney announced it would become the first non-Disney-owned children’s brand to feature in Disney Parks. A cornucopia of merchandise – from books and backpacks to child-sized electric cars – can be bought in almost every corner of the world. TikTok is obsessed with it. By some estimates, the brand is worth a cool $2bn.

“At every stage, Bluey has defied our expectations,” said Nicki Sheard, the CEO of brands and licensing at BBC Studios. But she insisted that fears Bluey was being over-commercialised were misplaced. “We want this to be a brand that is around for 100 years,” she said. “[But] the driving thrust of that is going to be maintaining that editorial authenticity and growing Bluey for the long term.”

So why has a cartoon depicting the everyday life of a family of Australian cattle dogs been such a huge hit with children and their parents? The Emmy and Bafta award-winning programme has an uncanny knack of pushing multi-generational buttons, said George Lewis, a comedian whose mention of Bluey in his standup show regularly provokes spontaneous cheers. “I think it’s just so real and so well observed and often unexpectedly moving,” he said. “I’ll be sitting with my toddler and find myself welling up. It completely catches you off guard.”

Like many parents who have taken tips from Bluey’s loving but imperfect parents, Chilli and Bandit, over the years, he is worried about Brumm’s decision to step away from the show, despite looking forward to the film. “It’s terrifying,” he said. “I’m so attached now that any changes are hugely worrying.”

On the fan sites, impassioned conversations look set to continue about the show’s future. Some are desperate to remain positive (“I have full faith in the team to keep the Bluey magic alive”) and some have urged restraint (“we gotta stop freaking each other out!”). Others, however, appear to be simply resigned. “Look, it was a wonderful thing that the world needed at a wonderful time and it will exist for ever,” wrote one Bluey fan. “It’s OK that this ends.”