In IT Chapter Two, Pennywise cruelly uses Georgie's form to taunt Bill about his brother's death with the phrase "you lied and I died." In all versions of IT, Georgie's murder at the hands (claws?) of Pennywise serves as the inciting incident that starts the Losers' Club on the path to a showdown with the ancient monster. The image of young Georgie peering down into the sewer looking for his paper boat, only to encounter Pennywise, has become iconic, and is the scene most closely associated with IT.
The rendition of Georgie's death found in IT 2017 immediately got noticed for how much more brutal it was than the corresponding scene in IT 1990, which cuts away before Georgie can really be damaged. The R-rated film version is much closer to Stephen King's book though, showing Georgie's arm getting severed in graphic detail. The guilt over Georgie's early death is also a constant source of despair for Bill in IT the book, as well as both of its screen adaptations. In many ways, it's the driving force behind every action he takes.
In the final trailer for IT, fans were intrigued by a scene in which Bill encounters Georgie (created by Pennywise), who repeatedly yells at his older brother "you lied and I died!" Each yell gets progressively more demonic, and many wondered what exactly that taunt meant. Sure enough, IT Chapter Two cleared things up.
IT Chapter Two: What "You Lied & I Died" Means
In the full version of the "you lied and I died" scene, Georgie (or at least the appearance of him) blames Bill for his death, arguing that Bill was only pretending to be sick on the day Georgie died, and in fact just didn't want to go out and play with him. By the way Bill reacts, it's obvious this Pennywise-conjured Georgie is telling the truth, and Bill really did make an excuse to avoid going along on the S.S. Georgie's first and last voyage. While any rational person would realize that Bill's actions don't actually make him any more responsible for his brother dying at the hands of a supernatural creature, his survivor's guilt makes him all too susceptible to the idea.
Compounding Bill's guilt is his inability to save another child from Pennywise earlier in the film, ending up forced to watch the boy be eaten in front of him. Thankfully, Bill is able to overcome his guilt and sadness, and continue the fight against IT. The Losers eventually win IT Chapter Two's final battle, but not without suffering great losses. Eddie is dead, Richie is heartbroken, and Stan's frustrating suicide note reveals he chose to end his life as a way of ensuring his friends' victory. For Bill though, the biggest loss will always be his brother George, a happy little boy who just wanted to sail a paper boat.