In short, the voice is an evil entity 'playing' with Kevin and Kaylee. Kaylee doesn't play by its arbitrary rules and is removed. The repeating cartoon disappearance shows exactly what the entity is doing to Kevin, tormenting and mutilating him over and over again for its own amusement, for 572 days and into infinity.

The Big Picture\n\n The movie delves into the theme of childhood abandonment or abuse, portraying the home as a place of terror and hopelessness.