Revealing mistake: When Phoebe punches Dr. Williamson, it's easy to tell that she doesn't really punch him.
Visible crew/equipment: When the sisters hide the chimps in the laundry cart to slip out of the hospital, the blue T-mark is visible on the floor at the bottom of the screen, before they peek around the corner and notice the TV. (00:20:15)
Continuity mistake: Near the end of the episode Piper is talking to her sisters in the parlor with her watch is on her left wrist and a bracelet on her right wrist. She goes upstairs to her room to cry and her bracelet and watch have switched places. (00:39:05 - 00:40:00)
Answer: "Hush, Hush, Hush" Paula Cole.