Stephen King fans just learning about real-life events that inspired Pennywise

Stephen King's 1986 horror novel IT has had a number of adaptations in the almost 30 years since it was first published. However, what they all have in common is that they have all centered around the terrifying clown, Pennywise.

The author began writing IT September 9, 1981, and finished December 28, 1985. But many fans might not know that Stephen was inspired to create the terrifying character after having his own 'creepy' experience with a clown.

Since the book was first published, fans have wondered what might have inspired the horror writer to create a character like Pennywise. Some fans have speculated that it might have been inspired by John Wayne Gacy, a notorious serial killer and sex offender who often dressed as a clown, who was sentenced to death in 1980.

However, King has never confirmed this. Instead, he has shared his own opinions on clowns and their 'terrifying' looks and how they often scare kids.

After finishing The Stand, King was walking across a bridge in Colorado when he imagined a troll like the one in the children's tale Three Billy Goats Gruff, though he imagined it living in a sewer system rather than under a bridge. He said the whole story "just bounced" into his head, in particular the fact that 'It' could shapeshift - often into a clown which many find terrifying, including King himself.

Appearing on Late Night with Conan O'Brien in 2005, King opened up about how he had been one of the many children growing up terrified of clowns.

"Let's talk about it, because you were one of the first people who had the idea that a clown could be a scary figure," Conan said.

"Did you find clowns scary when you were a kid?"

King went on to recall a time he went to the circus as a child, where he saw a dozen full-grown adults with pale white faces and 'blood red' lips painted on. He said sarcastically: "What's not to like?"

When asked further if he'd had a personal interaction with a clown that had left him scared, the author went on to recall the moment he met a 'creepy' clown on a plane.

The chilling tale took place as he was travelling home after visiting Cleveland, Ohio - the last stop on his first large-scale book tour. As the plane was pulling back, as it was getting ready for departure, before it pulled back in.

"The door opens again and Ronald McDonald gets on the airplane," King recalled. "He's fully dressed [as a clown], sits down next to me, because I attract weirdness, you know? I'm like a weirdness magnet.

"And I was so weirded out by that point, that I wasn't even surprised. Here he is, orange hair, orange shoes, the whole nine yards. He sits down next to me. Plane takes off, no smoking lights goes off, he pulls out a pack of kents [cigarettes], lights up."

The clown then ordered himself a gin and tonic, with King adding: "And you think, what if this plane crashes? I'm gonna die next to a clown."