It is established that Doug owns a bottle of Scotch, and he is shown drinking it. However, in the fifth season episode Window Pain (2002), it is shown that Doug doesn't like Scotch.
When Doug and Arthur discuss the loan for the media room, a glass suddenly appears in Arthur's hand, then disappears in the next shot.
When Arthur catches Doug watching the old footage, Arthur sits on the couch and leans back. In the next shot, he is sitting up straight.
When Danny tries to move the furniture and discovers it's bolted down, Spence flips through a magazine that goes from open to closed between shots.
Near the beginning, when Doug yells, "I'm going to kill him!" the blanket on Arthur's shoulders is rumpled. In the next shot, it sits smoother.
Doug redesigns the basement and puts a Jets fathead on the wall. However the fathead is located where the door is usually located (in other episodes). The door is now located at the foot of the stairs.
A fireman enters the house carrying an ax when it appears the fire is over.