Womb Raider - S4-E21
Visible crew/equipment: While Piper, Phoebe, and Paige are in the magical cage, the Dark Priest, the demons, and the Seer are all killed/vanquished, then when Piper kicks open the cage the sisters walk out, and we can see the black mic transmitter attached to Phoebe's waist, at her back on the right. (00:38:40)
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