Other mistake: After Piper tells Phoebe to get to know Dex well and fast because it may be the one sign Phoebe can't ignore, Piper ends the family meeting. In the following overhead shot as Piper walks out we can see her reflection in the wall mirror and it shows her long dark brown hair, but the problem is the reflection should be showing the "Jenny Bennett" golden blonde hair instead. (00:05:05)
Visible crew/equipment: While Billie is in the dorm room with her friend, Taylor, talking about the disappearances, when Taylor gets up and stands beside Billie, the pink tape mark (it's a toe box mark) is visible on Billie's seat. (00:07:20)
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