Continuity mistake: When the school janitor jumps from the roof then falls on a parked car, his head is turned to the right and it's obvious that it's a dummy. Two shots later, when Dr. Chafee puts his hand on the neck to take a pulse, the head is turned to the left and the body has changed position.
Continuity mistake: When Barbara is standing on the cliff, we see that is is cloudy and foggy all around her. When she looks down to jump, it is sunny along the bottom of the cliff. However after she looks up, it's cloudy and foggy again for the rest of the scene.
Revealing mistake: When the eye doctor becomes hypnotized to put the wrong drops in her own eyes, if you watch the bottle nothing ever comes out of it that could cause her to scream.
Continuity mistake: When Mara is one year old she has dark eyes. When she is older in the next clip she has blue eyes.
Suggested correction: She is also an alien. We don't know if those things work the way the human body does.
Continuity mistake: When the crew is fleeing the mayhem, DR Verner tells them to leave and that she will be right behind them - it is dark outside. In the next clip if you look at the windows behind her you will see daylight in the window blinds.
Revealing mistake: When the minister's wife drops the torch it sets her on fire, the camera pans up, showing she's completely engulfed. In the next shot you can see she's behind the flames and not on fire at all.