Coyote Piper - S3-E9
Revealing mistake: Prue knocked Piper unconscious in the cat fight (after the Coyote Dance), and asked Justin to carry her to the car. But when he is apparently lifting Piper up from the floor, you see Piper standing up by herself.
Coyote Piper - S3-E9
Revealing mistake: After Phoebe has her premonition in the mausoleum, she wipes away the dust from the crypt to reveal Cole's father's name. Just BEFORE they show her wiping the dust away, you can see the letters in the shot of her leaning against the crypt.
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