It

It appears to children as the thing they fear the most. Richie sees it as a werewolf and as a crawling eye. Eddie sees a leper. Bill sees it as the clown who killed George. Beverly experiences It as blood in her bathroom, which will require her to explain her fear to her abusive father. Stanley sees dead boys who represent the absence of natural order. Mike sees the giant bird because of the movie Rodan. In this way, the author invites readers to ask what their own worst fears are, and to imagine what shape It would take if It appeared to them, deepening the experience of reading the novel. 

Pennywise uses balloons to send messages and taunts to children, but also to lure them towards it. It asks George if he wants a balloon but can also send balloons floating against the wind to demonstrate that It does not have to obey natural law. It shows that is has been present by leaving a balloon tied to Mike’s reading lamp while he is asleep, and also to mock Adrian Mellon’s boyfriend after Adrian is murdered. Balloons are typically a symbol of fun that are inverted in It as a symbol of evil.