Just before the sisters say the sleeping spell, they close the living room door on the trapped dreams in the sun room. When the camera pans back to Leo, the door is open behind him.
When the tracer demon infects Piper and Paige with dream sand, he zaps Leo through a door that is supposed to lead to the basement. Leo, however, ends up in a closet.
When Leo's dream gets fulfilled when he gets to feel the baby kick the pregnancy transfers back to Piper, showing a very prominent pregnant belly. Just as the Tracer demon shows up to kill them and Piper turns towards him and blows him up, her belly is suddenly abundantly flat with her baby bump is missing entirely. When she turns back to kiss Leo after she blows up the demon, her pregnant bump is back.
When Phoebe is talking to Leo and the Sandman in the attic, behind her tall buildings are visible, as if the house were placed in a downtown area, even though the show has established its location in a different neighborhood and has shown the house across the street several times.
Near the end of the episode, while in P3, Piper says that Beth Orton is playing in the club tonight. However, this mismatches her lips, which say "tomorrow", not "tonight".
When Paige and Phoebe orb to the campsite to save the Sandman, the demon henchman sees their orbs approaching and says: "Witches!" But since orbing is strictly a whitelighter power, the demon would assume that the orbs were whitelighters, not witches.