Continuity mistake: When Phoebe is walking the Dwarf to the door after finding out Piper pulled the sword from the stone, he steps outside and goes into fast-forward, then stops and goes back to normal speed as he sniffs a flower. During this, in the background, you can see Phoebe, who freezes the whole time. (00:18:40)
Continuity mistake: As Piper is talking to Mordaunt at the Round Table, her fringe changes from in front of her face to behind her ear to in front of her face again.
Continuity mistake: When the sisters first see the lady in the lake, the demon off to the side throws a knife into her back, but the knife hits completely straight, as it would if the demon had been directly behind her.
Chosen answer: Her agent/manager negotiated a special billing as part of her contract. It distinguishes her from the rest of the cast, probably when she became a producer on the show.
JC Fernandez