When Piper gets kidnapped, Prue and Phoebe come downstairs wearing different clothes than what they had on in the scene before, upstairs.
When Piper is talking to Andy in the parking lot, the same guy on a cell phone walks by twice behind Piper.
Phoebe writes down two Chinese characters on her hand, then shows her hand to the others. The camera then cuts to another angle, and she's still holding her hand up, but there's nothing on it. Then the camera cuts to a close up, and the characters are on her hand again.
After Mark dies when Wong and crew set Mark's body on fire he is wearing black pants but when they are pouring the gasoline and through out the rest of the episode his pants are grey.
Piper picks up the invitations to Prue's birthday party twice.
Yama is the god of the dead and the underworld in Hinduism, which isn't one of the five religions recognized by Chinese government.
When Piper picks up the paper to see "PSYCHICS WANTED" circled, we see above that two ads for nanny positions. However, they spell nanny "NAANY" instead.
Phoebe has a premonitions in black and white and yet she knows that the car in her premonition was pink.
Just because we saw the premonition in black and white, doesn't mean Phoebe did. It may just be to distinguish it on the show.
When Prue, Piper, and Phoebe are in the kitchen discussing Mark being a ghost, Phoebe asks "How do we know he doesn't really belong in hell?" and Piper answers "Because we can see him. He's one of the innocents we're supposed to protect." But in later shows, they can see evil ghosts. However as he is the first ghost they have come across they have no idea that they can see all ghosts. They discover this later in this episode when they see the ghost of the killer.
Mark as a ghost can't turn on the television, but he can sit on a couch, ride in a car and has doors opened for him even though he should pass through all of these solid objects.
Mark, a ghost, bumps into a handrail as he and Phoebe are leaving the hotel where she's gotten a new job as a bar psychic.
When Andy falls to the floor after falling over the cart with the cakes the cream and fruits have already soaked the carpet for some time.
When Piper and Mark are talking in the living room and he first gets up, you can see his reflection. But after the camera changes to Piper with the blanket and back again, his reflection is gone.
When ghost Mark looks down at this body right after he is shot you can see dead Mark still breathing.
Piper and Phoebe are planning a surprise party for Prue, but leave the invitations in a drawer in the kitchen that Prue could go into and find at any time.
When Mark is murdered on-camera, there is no sound heard from that fired shot.
Right after Phoebe sits down on Prue's bed to talk you can see people moving in the reflection in the mirror behind Prue.
When Prue is introduced to Susan, she asks if Susan is Andy's sister. Prue and Andy have known each other since they were kids so she would know if he had a sister.