It is already one of the most successful horror movies of all time, which means lots of people certainly seem to be into scary clowns. But why is It a clown? The film shows that Pennywise the Dancing Clown can take on the shape of anything he wants — or it wants — but it spends most of its time as a clown. The movie never explains why it is that Pennywise likes to be a clown, nor does it make any attempt to explain what exactly It is. Thankfully, there's a book the movie is based on that delves into these issues in some detail.
It by Stephen King, the 1985 novel on which the film is based, is a mammoth book that's packed with details. In fact, the new movie — which is over two hours long — is based on just half of the book, while a planned 2019 sequel will go over the film's other half. The book gives lots more details on the origins of It, who is an ancient cosmic evil being — millions of years old — who hails from another dimension known as the Deadlights. The movie does include a brief glimpse of the Deadlights, but it makes no attempt to explain what it is.
It's true form can't be comprehended by human eyes, and the closest approximation is described in the book as a giant hairy spider made of orange light — a pretty far cry from a dancing clown. It feeds on humans to survive, and it vastly prefers the taste of flesh that has tainted by fear. That's the reason why It most often feeds on children, because they're easier to scare and because their fears are so visceral and real. A terrified child is the most delicious thing in the world to It, and that leads in to the clown disguise.
The main reason why It spends so much time as a clown is so it can entice children before terrifying them. For instance, with Georgie, It's first victim of the film, It lures Georgie to come close by posing as a fun and funny clown. Then, once Georgie's close enough, It shows its fangs to terrify him before eating him. As for the reason why King himself chose to depict It as a clown, well, that's because the author thinks kids are terrified of the circus entertainers.
"Clowns are scary," King said, according to Business Insider. "There's just no way around that. Clowns can be as angry as they want, and that's their right -- they're clowns! I mean, obviously they love kids. I came out in support of some clowns in Europe who asked me to say something nice about clowns because they go to hospitals and try to cheer up sick kids. I mean, if I were a sick kid and I saw a f—king clown coming, all the red lines would go off on my gear, because I'd be scared to death! So kids are scared of clowns."
The reason why It is a clown is because it prefers to both entice and frighten children, and apparently there's no better vessel for doing that than white makeup and a big red nose.