Other mistake: When Andy, Phoebe and Prue are in the attic figuring out how to vanquish the ghost of Alcatraz, pages starts flipping, the book opens up to the page where the truth spell is, and Andy finds out that Prue cast that spell on him. Later when he asks how much time Prue gave him to react, she says "a minute or two". But in the episode "Truth is out there" (1-8) it was first in Prue's office when she told him, and the clock on the wall shows that it's 25 past 5. And it was 8 o'clock when Prue cast that spell. So few hours later when Andy and Prue are at Andy's door, it's almost 8 o'clock and Prue says she needs the answer now. So doesn't Andy have more like few hours rather than few minutes to react?
Other mistake: When Piper and Mark are in the police parking lot she holds the door open for him to get into her SUV. When he gets in you can see the SUV go down from his weight in the vehicle. Ghosts are supposed to be weightless.
Other mistake: Grams says that if she died the girls would automatically get their powers; but they got their powers 6 months later and Phoebe had to read from the book of shadows first. Not really automatically.
From Fear to Eternity - S1-E13
Other mistake: No one, including the cops, seem to think that all the victims' hair turned white is strange, as if getting scared to death actually turned your hair white.
