Necromancing the Stone - S5-E21
Plot hole: Piper mentions that Grams banished the Necromancer "sixty years ago" at Patty's Wiccanning. Grams soon thereafter says that the Necromancer has had "almost seventy years" to regain his strength. However, Patty was born in 1950, and this episode aired on 5/4/03, at which time Patty's Wiccanning could not have been more than 53 years earlier.
Necromancing the Stone - S5-E21
Visible crew/equipment: When Piper hits the mirror after being thrown across the room by the energy bolt, look closely at the roof in the other room: a black rectangular hole with a stage light poking out of it is visible.
Necromancing the Stone - S5-E21
Visible crew/equipment: After Phoebe tells Jason that she'll go with him to Hong Kong in the morning, when it cuts to Piper and Paige looking out of the attic window, the reflection of a crew member is visible in the window behind the candles. (00:33:40)
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