Visible crew/equipment: As the energy being moves down the city sidewalk, we see its shadow on the concrete. Right beside that, however, we can also see the distinctly-shaped shadow of the camera.

Visible crew/equipment: When Stanley levitates the meteor with his brain power, the wires that actually lift the rock are very easy to spot at the top of the screen.

Revealing: In this episode's present-day 1963, the scientists view film footage said to have been taken "yesterday." But the rather obvious crowd scene stock footage is ten years old, featuring cars and clothing no newer than 1953.

Revealing: In the bakery, Will plays a lively tune on the concertina - without touching any of the button-keys necessary to play the notes.

Continuity: The window in the chamber door changes its size between shots. At first, we can see just Gwyllm's head. But then the window somehow grows so that his head and shoulders are visible. When the window gets smaller again, only part of his head is visible.

Visible crew/equipment: As the ship lands in the beginning, the wire supporting the model is visible at the top of the screen.

Plot hole: Andro has memorized "every detail" of Cabot Jr.'s life, including his mother's name, Noel. Yet when he travels to the past, meets Noel and learns her name, he still mistakes Cabot Sr. for Cabot Jr., who isn't born yet. Having memorized all those details, he would have known the moment he met her that Noel was Jr.'s mother. Andro's confusion makes no sense.

Revealing: When the alien posing as a human is exposed, the OBIT screen shows his "true" alien form while he continues to appear human to the naked eye. The actor in alien costume on the screen copies Jeff Corey's movements, but at one point rather badly shatters the illusion by forgetting to raise his arms when Corey does.

Continuity: When the lab equipment shorts out after the earthquake, the unconscious Major Brothers is lying with his head propped up against the wall. But when Hamilton reaches him in the next shot, he's suddenly lying flat and is nowhere near the wall.

Factual error: When the energy monster kills his entire research staff by stopping their hearts, Dr. Block brings them all back to life (with their minds and personalities intact) by installing pacemakers. But when the heart stops functioning, brain death occurs within minutes. For this to work, he'd not only have to operate on several people simultaneously, he'd also have to be the fastest heart surgeon on Earth.

Continuity: When Joey turns off the bathtub tap, we can see that the water is no longer flowing. But the sound of running water continues. And a few shots later, the water is flowing once more, even though Joey hasn't gone near the tub again.

Continuity: When Phobos sets up the time converter, the grid on his large round scope has a diamond-shaped pattern. But when we see it from his point of view, the grid comprises perfect squares instead, and contains numbers that weren't there before.

Continuity: Harvey peeks into the small hole in the box using his right eye. On the first view from inside the box, a right eye is indeed looking in. But when the monster appears, a left eye is peering through the hole. The shot cuts immediately back to Harvey, who still has his right eye pressed to the opening.

Factual error: The General brandishes a six-shooter pistol with an enormous silencer attached to it. He's a career military guy who should definitely know better, so he gets a failing grade in Basic Weaponry 101. Silencers don't work on revolvers.

Revealing: The injured Spain falls and tries to crawl away from the alien, leaving handprints in the dust on the floor. Just to his left, you can see several handprints already on the floor from previous takes.

Continuity: In the lab, the alien's arms change positions instantaneously between shots.

Continuity: The alien's torn spacesuit sleeve somehow mends itself, but then is torn again a few shots later.

Continuity: The cloth pillows stabilizing the moonstone on the lab counter change positions several times between takes.

Continuity: Dr. Brice's name tag is partially tucked under her collar when she's inside the lab. When she walks into the corridor, the tag has shifted position and is outside the collar. Later, back in the lab, the tag keeps changing from over to under her collar repeatedly.

Continuity: General Stocker falls into a lunar quicksand pit and starts to sink. One arm disappears beneath the sand, but in the next shot, both his arms are outstretched and waving for help.