Continuity mistake: In the shot where Leo gets his wings back, his eyes are brown, usually they are blue.
Revealing mistake: When Maggie Murphy climbs onto the ledge of the roof to jump off you can see the surface of the ledge dipping as if it was foam.
Continuity mistake: When Prue shows her sisters the article in 415 Magazine with her photo credit, in the closeup we see that Prue opens the magazine with the article and Maggie's photograph on the page to the right, but in the next shot facing Piper and Phoebe the magazine is folded open and they're looking at the page to the left with an entirely different page to the right. (00:40:40)
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