Continuity: In episode 4, the Doctor's bow shrinks from when he talks to Liz Shaw while in prison, to when he stows aboard a jeep later. In the DVD commentary, producer Barry Letts blames himself for this mistake.

Continuity: In episode 1, when the Doctor opens the garage doors with his 'door handle', note the two men in the background, the position of the car behind him and the white pillar. In the next shot, the men and pillar disappear and the car moves to a different spot. In the shot after that, the tanker truck is now parked in front of a pillar. You can see near the beginning of episode 3 that there are two entirely different buildings that the tanker had been filmed in front of.

Revealing: In episode 6, when the Brigade Leader shoots the Primord Stahlmann, he falls down but no bullet holes are made in his costume. Thanks to Producer Barry Letts for spotting this one on the DVD commentary.

Plot hole: The Brigadier says UNIT HQ is 'a Top Secret establishment'. It is, in fact so secret that it has a large sign outside informing the world not only of its function, but also the name of the commanding officer...

Revealing: In episode 3, when the second Doctor, the Brigadier and Benton emerge from the TARDIS, the doors are left completely open with the camera looking straight into them for a long time, revealing not only the emptiness of the police box shell, but also that there's a pair of secret doors on the opposite side to the entrance doors. These 'secret doors' come in handy during episode 4, allowing seven people to come out of the police box in the final confrontation with Omega. (Well, it is stated time and again that the TARDIS is "bigger on the inside than the outside". Now we know how that happens...).

Plot hole: After UNIT HQ disappears, you can see a patch of grass where the UNIT HQ used to be...but just exactly how can grass grow underneath a building?

Revealing: When the Doctor and Jo see Bessie in the middle of the rocky area, there is the white chalky substance from the ground on her wheels, indicating she was driven to the spot rather than being "transported" to the black-hole.

Continuity: The Doctor's big brown overcoat was taken by the regular Kaled army in episode one and disappeared. In episode six, the Doctor goes into the incubator room and comes out with his brown overcoat magically restored.

Trivia: Chief of Security Nyder wears an iron cross on his uniform which mysteriously disappears in episode 3 - apparently the producers felt it was too close a reference to Nazism so it was removed from the show. (Source: DVD commentary).

Revealing: Whenever there's a close-up of Davros, it's very easy to see that there's a gap around his mouth where the mask should blend in with the actor's face, but doesn't. This mistake was rectified, incidentally, in Davros' next appearance in Destiny of the Daleks.

Revealing: When the Doctor and his companion are running past explosions in the sand, you can see the scrape marks from where the effects team covered up the holes containing the charges.

Revealing: Right after Davros yells "The Daleks will rule the universe," in Episode 3, one of the Dalek operators accidentally starts to lift the top off his Dalek before the scene ends.

Revealing: When the Cybermen break through to the bridge, they brush against the door and it bends as if made of cardboard. It was supposed to be made of reinforced steel.

Continuity: The hole that the cybermen make in the door increases in size just before they step through it.

Factual error: As the spaceship approaches the Earth of 65 million years ago, the Earth looks very much like the present day one. Hasn't anyone heard of "continental drift"? The Earth's land masses of 65 million years ago were not where they are now. (This has been fixed on the DVD)

Factual error: The Cybermen sets four explosive charges around the outside of the door, yet only the middle part of the door is damaged...

Revealing: Episode - The Five Doctors. When a Cyberman's arm is sliced off by the Robot's shuriken, you can see his real arm bulging out at the right side of his body.

Other: Episode - The Five Doctors. The Cyber Leader is supposed to follow The Master's footsteps exactly in order to get across the chessboard. He doesn't. This cannot be classed as a character mistake because the Cyber Leader knew what was involved. I believe this mistake was caused by the actor not being able to see the chessboard through his helmet.

Continuity: Episode - The Five Doctors. After the Raston Warrior Robot has killed all the Cybermen, watch the dead Cyberman in the back right of the picture. His arm position changes as the robot teleports away.

Revealing: When Stotz cuts a hole in his ship's door, you can see that the inside of it is made of white polystyrene. They painted the outside of it but obviously forgot about the inside. Also listen to the sound it makes when Stotz punches the hole through - it sounds exactly like polystyrene.