Prue states that she and Piper were 1 and 3 when Phoebe was born, but when the girls went back in time in "That '70s Episode", little Piper and Prue were much older than 1 and 3 when Patty found out she was pregnant with Phoebe.
After Piper leaves the hair salon, she returns home. She gets out of her Cherokee and closes the door as a bride in a convertible passes by. In the next scene, Piper is seen standing with the door to her Jeep still open. She then slams it shut in frustration.
After Cole and Phoebe exchange the bags of books, one of the bags disappears. Phoebe comes out with Cole's bag and hands it to him but when she is going back inside, she doesn't have anything with her and he only has one bag.
We see a full moon. The next day there is a total eclipse of the sun which requires a new or dark moon.
When Leo removes the arrow from Christopher's side to heal the wound, the arrow appears to have gone right through the bandage that would have been placed on the wound afterwards.
When Piper and Leo are talking outside, you can see Brian Krause's mic through his shirt.
Right after Phoebe and Prue are talking and Phoebe puts on her eclipse glasses, Piper walks into the manor. As the camera moves and Prue and Phoebe run to the door to greet her a boom microphone descends into the shot momentarily.
It makes little sense that Piper lets the sorcerer's minion get away after the attack when she could have frozen and captured him so they could have milked him for information.