Harry Potter Theory: IT's Pennywise Is A BOGGART!

2. Riddikulus!

As anyone with even a cursory awareness of boggarts knows, the only way to defeat one is to laugh at it. To conjure up a counter image to the projection of fear that it conjures to scare its targets based on humour. To ridicule it, taking away its powers of fear and vanquishing it through laughter.

Fundamentally, the victim has to turn that victimhood onto the boggart, turning it into a figure of fun and amusement, with laughter out loud acting as its most devastating remedy. The whole transaction is based on the idea of forcing the boggart to assume a less-threatening form, to insist that it doesn't actually look like the thing it's trying to use to scare the victim.

The same is absolutely true of IT, as the finale of Chapter Two confirms.

The ultimate defeat of IT isn't simply by the strength of will, as the book suggested it was, it's reframed slightly in the films to be about forcing IT to take a shape that is less threatening. Because of the quirk that IT is limited by the form that it chooses to take - similar to how a boggart takes on the characteristics only of what it transforms into - the Losers are able to insist that Pennywise is no more than a ridiculous dancing clown. Nothing more sinister than that.

They ridicule Pennywise, taking away his power and effectively laughing at him until he's nothing more than a puddle of goo with a face. They have used their version of Riddikulus, using their own imaginations in conjunction with established lore to limit the "container" the creature takes on.

That is so similar to the logic of boggarts that it's almost startling.

There is still a question over Pennywise though. While it could be that his form suits the group, so IT can appear in a sort of "communal phobia" it's a little inelegant. A little self-serving to theories like this. But there is actually lore in the Wizarding World history that confirms a loophole that could explain Pennywise too...