'It: Welcome to Derry' Writer Andy Muschietti Reveals the Show Has No Connection to 'The Mist'

Fans who were convinced they had spotted a sneaky Stephen King crossover in It: Welcome to Derry are about to be disappointed. The eerie new HBO Max series may expand the mythology of Pennywise and nod to The Dark Tower and The Shining, but its creators insist one popular theory is simply wrong.

Ever since the first trailer dropped in September, viewers have been buzzing about the thick fog that rolls through the town of Derry. Many were convinced it was a direct link to The Mist, another of King's most famous horror tales.

The truth, however, is far less crossover friendly. 'There is no connection to The Mist,' show writer Andy Muschietti told Entertainment Weekly. 'I'm sorry to disappoint everyone with this.'

The Fog That Terrified Derry

The mysterious fog plays a major role in the season one finale, titled Winter Fire. It snakes through the quiet Maine streets as Pennywise launches one of his most chilling attacks yet, using it to abduct the entire high school student body.

The fog also blankets the frozen lake where both children and adults race to stop the creature from escaping its supernatural prison. Its presence is constant, suffocating and deeply unsettling, which only fuelled fan speculation that Derry was colliding with another King universe.

But Muschietti insists the fog has its own internal logic tied directly to Pennywise himself.

A Visual Language for Evil

According to the filmmaker, the fog is not borrowed from The Mist at all, but a deliberate visual choice to show how It expands its influence.

'You see it in episode four when Taniel is telling the story and the asteroid hits the Earth,' Muschietti explains. 'After the explosion, the Deadlights are surrounded by this smoky fog. We decided to make that the language of It's expansion.'

In other words, the fog is Pennywise made visible. It represents the creature's supernatural power spreading outward now that the forces containing it have been weakened.

'If it wasn't for the indigenous community in the 1600s, It would have expanded across the world,' Muschietti adds. 'Now that the cage is open, I wanted to convey visually that this force of nature is growing.'

Why It Cannot Be The Mist

Showrunner Brad Caleb Kane, a lifelong Stephen King fan who co-created the series with Jason Fuchs, says the theory falls apart on a key mythology point.

'For that to be The Mist, there would have had to have been a portal opened into Todash Darkness,' he explains, referring to the monster-filled void between universes in King's lore.

That specific gateway is central to The Mist, which tells the story of a small town overwhelmed by creatures from another dimension after a scientific experiment goes wrong. No such portal exists in It: Welcome to Derry.

A Dark Echo of the Original Novel

Kane also reveals that the fog is rooted in King's original It novel. In the book's climactic battle between Pennywise and the Losers' Club, Derry is hit by a catastrophic flood.

'That flood is a direct consequence of the psychic and spiritual power of the creature,' Kane says. 'Its fear and its anger create very specific conditions in Derry.'

The series mirrors that idea. The fog marks a moment of intense emotion for Pennywise as it realises the path is open to escape Derry and spread its terror far beyond the town.

For fans hoping for a crossover, it may be bad news. But for horror lovers, it means Pennywise is more powerful than ever.