Revealing mistake: As Mary, Sam, Jarvis and Andrew are speeding away from the TV station, one of the boys from the UFO crashes his bike head first into the car. This causes the boy to crash through the window. When he does this the window shatters like a plate glass window instead of the safety glass that is a standard to be used for vehicle windshields.
Revealing mistake: When Sam is attacked by the alien hiding on Mary's back (during their first intimate scene) he grabs a red-hot poker from the fireplace. The following close-up of him stabbing the alien, shows the poker to be made of rubber as it bends at the tip each time he stabs it.