Revealing mistake: "Death" sets up Hunt's demise by activating the pool's purge pump and running it at maximum (so powerful it can suck the internal organs out of a person). The purge pump runs for several minutes before Hunt drops his coin into the water and goes after it. Despite the purge pump running at maximum all that time there is no change whatsoever in the pool's water level.
Revealing mistake: When George and Nick are walking across the street from the hospital where the "guy in the cowboy hat" is recovering, you can see that there was a green screen being used. As they are walking across the street, they seem to be a different shade than the background and a couple seconds later, George is hit by the ambulance.
Revealing mistake: When Nick has his arm nailed to the wall behind the cinema screen, he sets off the sprinklers to put out the fire. After this he sits back down again, at which point his "nailed" arm and hand move slightly (an inch or two). This would not be possible under the circumstances.