Continuity mistake: When Adam spills coffee all over Phoebe's top in the office, the stain disappears and reappears between shots. (00:08:05)
Continuity mistake: After Piper puts Little Red Riding Hood's cloak on and travels into the book we see a close up of the book and the cloak is still lying behind it. (00:36:50)
Continuity mistake: In the teaser Piper is reading a fairytale book to her unborn child. When Paige walks in we get a glimpse of the book, and both pages are filled with words. When Paige walks out and we see the book again, the right page of the book has a picture on it. (00:00:15 - 00:01:35)
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