Other mistake: At the beginning of the episode, when the mermaid goes underwater, she holds her breath.
Other mistake: If all the objects in the fortress are originals from the fairy tales, why are the ruby slippers red? In the original story the slippers were silver, they were made red for the MGM movie, so they would be the brightest thing on the screen.
Siren Song - S5-E4
Other mistake: When the siren gets the pole that was speared through her pulled out, there is only blood in the middle part of the pole. If it had really been pulled out of her, it would be bloody all the way along. (00:19:55)
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