Visible crew/equipment: When Phoebe and Paige are trapped against the wall/stairs by the web, the seat that Paige rests on is visible, together with supports under her feet - also note the decorative stair baluster has been removed.
Continuity mistake: When the spider demon cocoons Piper, Paige throws a blue potion (the vanquishing potion) at her, Chris catches it and jumps over the couch, knocks Paige to the floor and Phoebe kicks Chris. The potion falls out of Chris hand and rolls into Paige's open hand, it has now turned yellow (the antidote) Paige grabs it as she stands and throws it at the spider demon again and it has now turned back into the blue potion.
Continuity mistake: When Paige is at P3, her mobile phone changes positions between shots.
Continuity mistake: After Chris seals up the cave, he is walking towards Leo. Look in the background and you will see the Piper cocoon. How can this be, because after the spider demon is killed, we see Piper is ok. (00:33:35)
Revealing mistake: When Piper is being spun in the web, she spins around and gets stuck to the wall. If you look closely Chris's eyes look above the CGI figure and do not follow it correctly.
Continuity mistake: When Chris's hand gets stuck to the first aid kit, the position of his hand changes between shots.
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