Gone With The Witches - S8-E20
Continuity mistake: When the leprechauns are called back to the manor from Magic School, O'Brien cradles his injured arm in his left hand. In the next shot, his arm is down by his side and he moves it to his arm again. (00:25:10)
Plot hole: When Piper goes back in time to save her sisters from dying and get rid of the Hollow, right after Leo describes it as "time catching up with itself" and the new reality Piper takes over her body. Yet in Season 5 Episode 7 "A Witch in Time", Piper goes back to keep Phoebe from saving her boyfriend but once Piper changes the past, the original Piper fades away and the new reality Piper stays.
Plot hole: In the final episode Piper cast the spell with her mother Patty and grandmother Penny to get the Hollow out of (past) Piper, Phoebe, Paige, Billy and Christy. It worked. But in episode 4x13 Charmed and Dangerous, the only way to contain the Hollow is by good and evil working together... which wasn't the case in the final episode.
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