During Max's magic act on Halloween, Max's red-headed brother can be seen sitting next to his mother in close-up shots; however, in far-away shots a different boy with brown hair is sitting next her. It appears that both boys are wearing the same wardrobe though. Furthermore, the man who helps Max with his card trick is seen sitting to the left of Max's parents in close-up shots but in far-away shots he is sitting to their right.
When young ghost Tara runs in front of Colin, the human older brother, while Colin and his dad are watching TV, Tara hits the bowl of popcorn on the coffee table and the bowl visibly moves. Earlier the film had established that ghosts would pass through anything solid unless they concentrated on that object to be moved. (In this case, Tara was not concentrating on the bowl.) Furthermore, the bowl had been in Colin's lap a moment before when it suddenly appeared on the coffee table. Immediately after Tara knocked the bowl aside, the bowl appeared back in Colin's lap in the next shot.
In Max' magic act fantasy, he covers Traci with a sheet. The top of the sheet is rounded due to the shape of her head, but when the camera changes, her covered "head" is pointy due to the invisible strings holding up the sheet with Traci no longer under it.
When Colin hits himself in the face with a tray of peanuts, it bends proving it is plastic but he passes out as if it were real.
Boom visible in the bottom left hand corner as Max is running up the three flights of stairs to catch the girl.