Revealing mistake: When Prue talks about her relationship with Justin near the beginning of the episode, she says that she finds him to be very predictable, lacking in mystery or "savoir-faire." That doesn't make sense, though, as "savoir-faire" means "know-how." She probably meant "je ne sais quoi," that is, "I know not what."
Continuity mistake: While Dantalian tries to steal the Book of Shadows from the attic Piper and Phoebe surprise her, then when Phoebe kicks Dantalian and she falls we see the stuntwoman's footwear has chunky sole ridges, but when the sisters approach Dantalian her shoes have heels. (00:32:10)
Audio problem: When Evil Prue flings Piper and Phoebe back, you see Piper hit a pillar, but with Phoebe's voice of pain. When we see Phoebe fall behind a structure, we hear Piper's voice of pain.
Answer: "Hush, Hush, Hush" Paula Cole.