Melinda tells the sisters that Matthew must have copied the blinking power from another witch. Throughout the rest of the series, blinking is a warlock power, not a witch power.
The locket twists around between shots after Melinda Warren puts it back on.
After Prue lets Matthew out of the locket in her office, her hand keeps moving from at her side to on her stomach between shots.
After Matthew is released, he breaks the window and lowers himself to the ground. Everyone in the Cafe seems very calm but they should already be very surprised and upset by broken glass raining down from the window above... The broken glass seems to have just disappeared...
Their ancestor, Melinda, is said to have been burned at the stake during the Salem Witch Trials. Every woman executed in the Salem Witch Trials was hanged.
The potion for the vanquish spell, the one that Melinda used in Salem 300 years previously, requires a feather from an endangered spotted owl, which makes it difficult for the sisters to make the potion. There weren't any spotted owls, endangered or otherwise, on the East Coast where and when Melinda came from.
It is mentioned that Melinda Warren was burned at the stake in Salem. In fact, no one was burned to death in Salem. Those sentenced for witchcraft were actually executed by hanging; one man died as a result of torture by being crushed by rocks.
When Andy is looking for Prue, Phoebe asks him where his warrant is. The police don't need a warrant to question people. Warrants are only for arrests and searches.
Original goof: "Matthew and Melinda Warren are surprised by many aspects of the modern world, such as photographs. Yet when Matthew is given a semi-automatic pistol, he seems to know what it is and how to use it without explanation." However, it's almost certainly a probability that Rex showed him how to use the gun.
Prue gets away from Andy by setting off the driver's airbag, trapping him in the car. In reality, airbags inflate and then deflate in a fraction of a second.
However, since she used magic to inflate it, she should also be able to keep it inflated as well.
Melinda Warren makes the comment about the Book of Shadows having gotten so thick. But she was burned at the stake in 1692 and, according to its first page, the Book of Shadows wasn't started until 1693, so there's no way she could have known if the book was always that thick or not. However, just because the first page of the Book of Shadows says 1693, doesn't mean that the original spells weren't from before that date. There is the possibility that Melinda's daughter, or other descendants, added that page to the book at a later date. Not to mention that the Book of Shadows would never have been in such an ostentatious binding when it was first put together.
When Piper sets the pitcher of iced tea on the counter after offering Leo a glass, the ice cubes are swirling around the bottom of the pitcher, revealing that they are not real ice cubes.
Leo quotes Shakespeare and Melinda finishes the sentence, however his work wasn't know abroad until the 18th and 19th centuries.
Right after he leaves Prue's office, Mathew seems to know about phone books (he has a torn out phone book page in his hand) and addresses and seems to have found his way around San Francisco quit well with no experience of a large modern city.
Rex tells Hannah that worrying will give her wrinkles on her horns. Later in the series, Hannah's demonic form is shown to be a panther, an animal without horns.