When Bud enters the living room with all the equipment he needs to create a "fake tornado", he can be seen wearing a ring on both his ring finger and pinky finger of his left hand. After a cut to Kelly and back to Bud, the rings are gone for the remainder of the episode.
Al obviously misses when he "punches" Jefferson. However, that "fake punch" is so obvious it might be a coincidental reference to the same error made by James Caan in "The Godfather" (1972).
Ariel punches/slaps Bud several times. The first time she hits him, the sound doesn't match the action.
Obvious stunt double when Marcy comes falling down the basement stairs.
Obvious stunt double when Bud comes falling down the basement stairs.