It Chapter 1 & 2: Every Monster Explained & Ranked
6. Georgie
The OG haunting in It is the most important in terms of the sequel's obsession with suppressed memory and how Pennywise is able to get a hold on the minds of his victims. He manipulates them into believing they were at fault for their traumas - that Mike made his parents die, that Bev brought her abuse on herself and most pertinently that Bill ensured George died through his own actions.
George also represents Bill's means of dealing with trauma - confrontation. It's a rather inelegant expression of it, but it works - Bill has to come to the conclusion that what he did didn't directly lead to Georgie's death and that he can't blame himself. At the same time, he has to sort of accept that he did play a part too, but he can't keep reliving it or he'll be reliving a cycle similar to Pennywise's "bouncing back."
There's always something more profoundly affecting about child ghosts and angry ones that blame those they're haunting for their deaths are extra spicy as George proves. Even without the need for silly CGI, he's right up there as one of the most chilling presences.