Question: In the opening credits, Holly Combs is credited with "and Holly Marie Combs as 'Piper'". Why was she credited with her character's name, when none of the other three lead actresses were?
Answer: She became a producer.
Incorrect. Her billing changed in season 4 but she didn't become a producer until season 5.
Unrest at the Nursery! - S15-E47
Question: Why did Vullaby run away from the nursery? Was it because of Layla hurting her feelings?
Answer: Yes it ran away because Layla hurt its feelings.
Moral Decay / Meet The Beat Alls - S3-E13
Question: There is something I don't get about Buttercup in this episode. She's a hero. Why would she knock some teeth out just for some money? That sounds like something a villain would do.
Answer: Buttercup is a hero, but she is also a 5-year-old child. She still needs to learn the same moral lessons any other child would. The girls often make the same questionable decisions regular kids do in real life, taken to an extreme because they have super powers and fight crime. Also, this is a highly stylized and over the top show where character traits are regularly exaggerated for a laugh.
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