Visible crew/equipment: After the Grimlocks enter the manor Leo calls for Piper then rushes out of the kitchen, and when it cuts to the shot of the dining room the edge of the crew's black mat is visible at the bottom of the screen. The black mat is again when the sisters are pulled into the time portal, though the only thing we should be seeing is the fringed area rug. (00:04:00)
Other mistake: Approximately four minutes into the episode, two demons go to the manor. Pru catches them and "throws" them to the one side. Her arm motion would fling them to the right, but they fly to the left. (00:04:15)
Plot hole: When Phoebe and Cole are using the apple peel to find out her true love how does she not recognize that it is Cole? Even with the mask it's very clear that it is him.
Suggested correction: I was thinking the same, but it's possible she thought he was an ancestor/past life of Cole. When she visited her own past life, she recognized everyone there because of their "souls" so maybe she thought the same with him. Although you'd think they'd acknowledge that a little.
Revealing mistake: When Leo dropped the Grimlock potion, it was obviously fake when it hit the ground.
Continuity mistake: When Piper and Prue are standing in the bedroom with Charlotte, Prue's hand moves from covering her mouth in one shot, to being by her side in the next.
Continuity mistake: In the scene where Eva is teaching the sisters about ways to draw power on All Hallows Eve, she cuts an apple in half and puts a leaf over the seeds in the center. The leaf goes from small and only covering the center to bigger and covering more of the apple.