Pennywise the Clown is not a clown at all. The Pennywise the clown origin story sees an ancient, evil being that is perhaps as old as the universe itself. In the novel, however, the entity IT/Pennywise has a real name — Bob Gray. Bob Gray isn't human, however, and shares the same origin as IT.
In the novel, It's origins are nebulous. He took the form of a clown most frequently, Mr. Bob Gray or Pennywise, but his true form is an ancient eldritch entity from another universe who landed in the town that would become Derry by way of an asteroid and first awoke in 1715.
In the novel, It claims that its true name is Robert "Bob" Gray, but decided to be named “It”. Throughout the book, It is generally referred to as male, usually appearing as Pennywise. The Losers come to believe It may be female after seeing it in the form of a monstrous giant spider that lays eggs.
The backstory of Pennywise is tied to an ancient cosmic entity referred to as the "It" or the "Eater of Worlds." This entity is from another dimension and has existed for an extremely long time. It comes to Earth approximately every 27 years to prey on the children of Derry.
After the Losers show Pennywise they're not afraid anymore and are ready to fight it, the clown takes some hybrid forms to try to scare the group: Pennywise/burned arms for Mike, Pennywise with the head of the woman from the painting for Stan, Pennywise with spider legs, Pennywise with the head of a mummy for Ben, ...
The movies have a different approach when it comes to the Pennywise the clown origin story, with IT's name being Robert "Bob" Gray. In IT: Chapter 2, there is a lengthy exposition section explaining the origins of Pennywise the Dancing Clown. There was a human Pennywise the Dancing Clown, but IT just takes his form.
Stephen King's IT introduced readers to a one-of-a-kind creature that can take any form, the most common one being Pennywise the Dancing Clown, and as menacing as it is, this creature has one big enemy it's truly scared of: Maturin, the turtle.
In both the book and the films, It is an ancient alien creature, older than civilization, and in King's novel, older than our universe. It feasts on the flesh of humans simply because our fears are easy to manifest and they make us taste better.
Georgie Elmer Denbrough is a fictional character created by Stephen King from his 1986 epic horror novel It. Georgie is the younger brother of Bill Denbrough, and falls prey to Pennywise the Clown. He is used by Pennywise to taunt Bill throughout the novel.
Pennywise pretty much made Derry the perfect place for a creature like itself to live, and with the whole town under its control and with a lot of children (and adults) to feed from, IT didn't really have reasons to leave Derry.
But, the film makes clear, It (sometimes written as “IT”) isn't just a clown. Oh no. As detailed in King's novel, he's an ancient, cosmic being, described in the novel as an “Eater of Worlds”, who is able to adopt a variety of nasty guises.
Throughout Stephen King's It, Pennywise is referred to as a male, but author Stephen King pulled a fast one on readers in the It book ending by revealing the creature's true form was a pregnant spider, implying that it is, in fact, biologically female.
And if his victim believes him to be powerless, he will become powerless. And so the group figures out that their best bet is, essentially, to bully the bully: They mock Pennywise, telling him he isn't scary. Humiliated, Pennywise begins to shrink, transforming into an almost Benjamin Button–like, melted clown-baby.
Pennywise targets children instead of adults because they are easier to scare and manipulate. Their fears are often simpler, more direct, and easier for Pennywise to exploit.
Now, King doesn't offer an explanation as to why Pennywise is named like that, and the name doesn't seem to have any cultural significance except for the old English saying “Penny Wise, Pound Foolish”, which refers to being stingy about less expensive things but not so much on big things.
A neighbor witnesses his disappearance, but the fact his body is never found gives Bill hope Georgie somehow survived. Pennywise prays on this in the film, using that hope to lure Bill in the finale. Bill later finds the tatters of Georgie's coat and finally accepts his brother is gone.
Luke Roessler portrays Dean, a young boy who meets Bill near the storm drain where Georgie was killed in 1988, and who is later killed by It at the Funland.
Pennywise had targeted Georgie when the boy was too young to know any better or fight back. In the clown's most contemptible murders, Pennywise did not rely on visions or fears to lure Georgie in; instead, Pennywise exploited Georgie's trust and turned it into a fatal weakness.
They reach the conclusion that Pennywise has all of the adults under some sort of spell that prohibits them from seeing him. The adults of Derry are shown to be villainous in their own right as well. The adults of Derry are shown to be true villains of the story in the same way as Pennywise.
IT arrived on Earth through an event similar to an asteroid impact, landing in what would later become Derry, Maine. Once there, IT adopted its usual pattern of hibernation that lasted between 27 and 30 years, awakening to kill and eat and then going back to sleep.
While playing Pennywise in IT and IT Chapter Two, Bill Skarsgard wears a set of prosthetic teeth, for times when the dancing clown really needs to show off his razor-sharp chompers. The problem is, these teeth caused Skarsgard to drool, and not just a little. The teeth caused full-on torrents of slobber from the actor.
If you want to get technical, It is an alien, but It's origin goes well beyond that. It is actually an ancient cosmic deity. A god of destruction, not just of our world, but of multiple worlds and even multiple universes.
IT is a shape-shifting creature known as a Glamour who is billions of years old. Although it lived on planet Earth for many years, Pennywise originated in a void/dimension outside the regions of space known as the Macroverse.
It describes that it prefers to kill and devour children, not by nature, rather because children's fears are easier to interpret in a physical form and thus children are easier to fill with terror, which It says is akin to marinating the meat.
