"The Losers Club" becomes aware of Pennywise's presence because of Bill's little brother, Georgie. King stated in a 2013 interview that he came up with the idea for Pennywise after asking himself what children feared "more than anything else in the world", and feeling that the answer was clowns.
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.
Well, that's not super easy to answer, but let's give it a try. 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.
It's primary goal is to feed on humans, generally preferring children over adults since they were easier to scare and manipulate. According to the creature, frightened flesh tastes better and uses fear to "salt the meat".
Pennywise is Older than the Universe Itself
According to the novel, Pennywise existed long before The Big Bang in a dimension known as Macroverse. After crash landing on Earth, he entered a state of hibernation and awoke in early 18th century America to sustain himself on human victims before returning to his slumber.
Almost certainly the most well-known evil clown (save for Batman¹s archnemesis, the Joker; more on him later), Pennywise is modeled after real-life serial killer John Wayne Gacy, aka Pogo the Clown, a.k.a. "The Clown Killer." Gacy was convicted of sexually assaulting and killing 33 boys in 1980; he posed as a clown ...
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.
However, It must surrender the the laws of whatever shape It takes. Pennywise's strength is also his weakness. For example, if he were to take the shape of a werewolf (as he does in the novel), silver bullets would harm him.
Also in the 2017 film, Georgie's death is changed. As well as having his right arm bitten off, Georgie is trying to crawl away but he was dragged into the sewers and devoured by Pennywise, with an unnamed older woman and her cat being the sole witnesses of the horrific scene, including before Georgie lost his arm.
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.
The turtle is a force of benevolence and is guided by compassion, whereas IT represents chaos, evil, and fear. They are diametrically opposed. Because they are both interdimensional entities with equal powers, the turtle could kill IT if it wanted to, therefore it's understandable that IT is terrified of it.
Originally Answered: Why did Pennywise start on Chapter Two with attacking an adult? Pennywise thrives on fear. By killing him, Pennywise gets the town starting to fear others. Setting the stage for his return.
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.
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.
The cinematic adaptation of Stephen King's It Chapter Two depicted the satisfying death of Pennywise while subtly hearkening back to Pennywise's first 1988 victim, Bill's brother Georgie.
It was said on page 1361 that the Spider being both female and pregnant was a symbolic interperetation. Its not literal, but a representation of whatever equivalent but inconceivable reproductive capability It actually has. Pennywise didn't become pregnant.
Pennywise uses the Deadlights to break a person's mind because one look at the Deadlights will make a person go insane due to it not being able to be comprehended by a human mind.
The children are bullied because of Pennywise, not that he especially singles them out. The entire town of Derry is essentially infected with ITs evil. That's why children are bullied, parents are abusive, and adults seem not to see the rampant dysfunction around them.
This is one of the most interesting Hollywood couplings we learned about in quite some time. Apparently, Pennywise and the Babadook are dating. In fact, they're in a long term committed relationship.
The spider-clown shrinks as the Losers hurl taunts at It, until it's tiny and weak enough that they pluck out its heart and squash it into nothingness. In the end, they defeat Pennywise by, uh, making him feel really bad about himself.
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.
It Chapter Two more explicitly suggests Pennywise was an actual clown who may have been possessed by It, just as Henry Bowers is in the movies. This is implied when Beverly Marsh (Jessica Chastain) visits the apartment she grew up in with her abusive father.
In Stephen King's novel It, Maturin communicates with Bill, the leader of the Losers Club, and helps the Losers Club defeat It by lending them strength. It comes in many shapes and sizes. Most iconically, It takes the form of Pennywise the Clown, whose real name is actually Bob Gray (anticlimactic, honestly).
After his death, Pennywise begins disintegrating and his underground lair collapses as well, forcing the Losers to escape – but they're forced to leave behind Eddie, who was mortally wounded by It earlier in the battle and died.