Continuity: At the end of the episode, when Prue shuts the door magically it shows the inside of the house. There should be a doorway parallel to the front door that leads from the foyer into the dining room, but instead there is a wall.
Great sites
Quotes
Phoebe: Woman to woman, okay. Cole was the love of my life, and I'm finally learning to live without him. Calling him for a favor would open a can of worms that I've been trying to close.
Elise: Woman to woman. If you're still describing this guy as the love of your life, then the can is open, the worms are out, and you may as well use them to go fishing.
Trivia
Many actors who have made appearances on Charmed have also made appearances in Buffy. Some are Greg Vaughn, Charlie Weber, Wade Andrew Williams, Kevin Weisman, Christopher Wiehl, Daniel Dae Kim, Michael Bailey Smith and Brian Thompson. See more...
Charmed (1998) - 3 mistakes in "Be Careful What You Witch For"
starring Alyssa Milano, Brian Krause, Holly Marie Combs, Rose McGowan, Shannen Doherty (add more)
Updates: 
Series 4
Be Careful What You Witch For (season 2, episode 22)
Continuity: When Phoebe and Piper are leaving to go get Prue, Piper kisses Leo on the cheek and there is a lipstick mark on his cheek. Then the shot goes to Piper then back to Leo, and the mark has gone with no time for him to remove it.
Continuity: When Piper and Leo find the genie at the restaurant, look at the girl in the background, when Piper freezes the time, first she's talking to someone, then she's looking at a menu.
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