In the beginning of a scene where Doug is at the dentist, the first shot is a close-up of the dentist aggressively and uncomfortably handling Doug's mouth. However, you can tell by the angle of the forearms in the frame and the way Doug's shoulders move, it's actually Kevin James doing this to himself.
Doug and Carrie bump into each other as they walk through the neighborhood in the opening scene. However the neighborhood that they are walking through is in Brooklyn as the background shot has the view of the Verrazano Narrows Bridge. Of course they could both be walking around Brooklyn but that would be quite the coincidence to bump into each other at that spot.
Arthur becomes a Piano Teacher to Deacon's child. But Arthur can't play the Piano. But in a much earlier episode we see Arthur playing the piano with skill.
The Heffernans have a piano, which is central to the plot of this episode, yet no one plays the piano.