"This isn't real enough for you, Billy? I'm not real enough for you? It was real enough for Georgie!" - Pennywise
No one knows the true form of It since it exists in an inter-dimensional realm referred to as "deadlights". Bill Denbrough comes close to see the "deadlights", but defeats It before this happens.
From Stephen King's IT, Pennywise with Spider Legs, as a stylized Pop vinyl from Funko! Pop IT Pennywise Spider Leg Vinyl Figure #542 stands 3 3/4 inches and comes in a window display box. Collect them all!