Sand Francisco Dreamin' - S5-E14
Visible crew/equipment: After Phoebe returns with a bowl of dream dust from the remains of the Sandman, Phoebe opens and closes the door to the conservatory to view their three dream guests, then as they all turn and walk toward the sofa we can see the reflection of the moving boom pole and mic in the mirror. Also, note the door that Phoebe had closed is now wide open in Leo's closeups. (00:32:15)
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