Destiny of the Daleks - S17-E1
Deliberate mistake: The shot of the alien spacecraft flying in the sky is the same in episode 4 as in episode 1, only it's reversed. The taking off and landing are the same too, except smoke and rubble have been added.
Revealing mistake: When the Morbius creature falls over the cliff, he bumps into the camera.
Revealing mistake: Jo is hit by a rather large rock. Katy Manning visibly winces before it strikes (and bounces off lightly).
The Invasion - S6-E3
Revealing mistake: The Cyberman that falls from the roof in the final episode is obviously an empty costume. (This is another example of a mistake being repeated from an earlier episode. See the earlier story "The Tomb of the Cybermen" for a note about the same 'revealing' mistake happening).
Factual error: How did potatoes come to appear in a 12th century kitchen? The potato was unknown in England until Sir Walter Raleigh brought them from back from the Americas on one of his voyages in the late 16th century, at least 400 years after the period in which this story is set.
Audio problem: In episode 3, when the dog is barking at Sam's house and is abruptly silenced (apparently by an Auton), the sound is obviously not a dog barking. It sounds a bit like a man pretending to be a dog, and going "woof woof" not very convincingly.
Continuity mistake: The rhyme the Doctor recites in episode 3 is different from the original rhyme heard in episode 1. (Apparently, the Doctor [William Hartnell] forgot his lines in episode 3, when he came to the point of reciting the rhyme. So he just improvised what he thought they were, rather than what had been scripted).
Continuity mistake: At one point in the story, the Doctor hurriedly types out a letter to leave for the Brigadier and Sarah Jane, and pins it to the TARDIS. Later when Sarah Jane reads the note, you can see it's been handwritten.
Factual error: Billy Claiborne, the only member of the Clanton gang to survive the O.K. Corrall shoot-out, is conspicuous by his total absence in this story. Maybe that's how he survived?
Plot hole: It is never explained why so much of the story takes place in England. All of the equipment for Sutekh's rocket comes from his tomb and could just as easily - probably more easily - have been set up right there in Egypt. And at the end, instead of just walking out of his tomb, he takes the spatial corridor to England just so he can get caught in the Doctor's trap.
The Trial of a Time Lord 5-8 (aka Mindwarp) - S23-E2
Continuity mistake: When Kiv wakes up in Peri's body, (s)he orders Crozier to kill the body Kiv was using before. Crozier responds that it's already dead, but in the previous shot the old body could be seen breathing.
Plot hole: The sketch of Romana is different when it's seen outside the café from the one seen inside the café (and just who's doing the sketch, and why?).
The Dalek Invasion of Earth - S2-E2
Revealing mistake: When Barbara, Jenny and Dortman are running through the deserted streets of London, in the very last shot, if you look to the left of the screen, you can see some people walking down the street.
Revealing mistake: When SV7 comes into Taren Capel's workshop, its usual eyes are missing - only black discs are visible (later in the scene, these are overlaid with the red speckled pattern to show the robot being reprogrammed).
The Caves of Androzani - S21-E6
Continuity mistake: When the Doctor and Peri first land on Androzani, mountains are seen in the background. They disappear when Peri picks up the silica. A couple of shots later, they're back. (This mistake was mentioned on the DVD commentary; the mountain effect was left out for financial reasons).
Continuity mistake: When Frankenstein's Monster begins chasing The Daleks, he's wrapped in bandages. When he catches The Daleks in the room with the TARDIS, he's suddenly wearing a suit.
Continuity mistake: In episode one, Vicki passes her hand through a museum display, making the point that the crew cannot interact with their environment. A moment later, she bumps into a statue, making it wobble.
Visible crew/equipment: As the Doctor is watching Will emerge from the priest-hole, look over his shoulder at the far corner. Someone or something appears to be moving in the shadows there.
The Caves of Androzani - S21-E6
Visible crew/equipment: The boom mike is visible at the top of the screen when one of Jek's androids is handing spectrox to the mercenaries. The shadow of the boom pole is also visible on the roof beam.
Other mistake: In episode two, when Poul enters the room where Uvanov and D84 are holding Leela, the body of Cass breathes.
Answer: It was never destroyed on-screen; it was intact at the end of the TV movie, and destroyed by the start of the 2005 series. It was destroyed in the novel "The Ancestor Cell," but in a completely different manner to what happened in the series.
DaveJB