Factual error: PJ is getting his hair cut by an attractive female barber. Attached to the outside of the window is a neon sign reading "BARBER SHOP," but the sign faces the inside of the building so it would be backwards to people outside.
Other mistake: When PJ tells Gabe about the attic, he said he had never heard of the attic. But in the earlier episode "Charlie Shakes It Up" Amy tells Gabe to clean out the attic while she's away.