While some children are able to blame a sibling for their own wrongdoing, things become a little more complicated when you're an only child.
In Liam's case, his use of the bathroom walls as a canvas forced him to think quick on his feet once his parents discovered his artwork. Rather than immediately accuse the boy of writing his name all of the bathroom, his father allowed him to describe the "monster" and recount his vandalism.
Maybe Liam can think of a better story while he scrubs the walls.