Visible crew/equipment: When they're all practicing the Charleston, while Bobby's watching from the stairs, everyone is shown dancing from different angles, and in the low angle shots facing the kitchen the top of the kitchen set is visible, particularly when Carol twirls her necklace.
Visible crew/equipment: As Mike gets up from the table after lecturing the girls, the boom mike's shadow becomes visible on his back. (00:15:00)
Answer: The dangling bracelet was used for dramatic purposes - to keep the audience on edge.