Revealing mistake: When Phoebe goes to sign her papers at the end, she spells her name as Pheobe. (01:22:45)
Revealing mistake: When Piper blows up the painting you can see the hole used to put the charge into to blow it up. (00:57:40)
Continuity mistake: When Paige goes to Cole for help saving Phoebe, she puts her hand on his chest. In the next shot, her hand disappears, with no time for her to have moved it. (01:11:35)
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