Continuity mistake: When Leela attacks the guard near the computer complex in episode three, his gun goes flying down the hall. But she then picks it up right next to his body.
Continuity mistake: When the TARDIS breaks apart and the console sent spinning off into space, Zoe is lying on it. In close-ups she lying on her left side facing towards Jamie (who is opposite), but in the distance shots done with small models, she is lying on her right side facing away from Jamie.
Continuity mistake: In episode 3, when the Doctor leaves the old house to find the dynamite, you can see his hat resting on a chair as he walks out the door. Immediately afterwards you see him walking through the woods with Sarah, and see that the hat has magically relocated itself to being back on his head again. And when he eventually gets back to the cottage, the hat is there, still in the chair as if nothing had happened.
Continuity mistake: In episode four, when the Doctor is patching the communicator into the android's head, he takes off the communicator's top, yet it is back on a few seconds later.
The Ambassadors of Death - S7-E3
Continuity mistake: Taltalian's French accent mysteriously gives way to an English one in some shots, most notably on location, e.g. when he catches an escaping Liz and says "Get in Miss Shaw".
The Curse of Peladon: Episode Two - S9-E6
Continuity mistake: As Jo walks along the castle ledge to escape from The Ice Warriors' room, there is, at one point, a quick shot of a piece of the ledge breaking off under Jo's shoe and falling down the cliff face. However, the shoe isn't Jo's. If you look closely, you'll see that the shoe in that brief shot is more pointed and of a darker colour than the shoes Jo is wearing, and has a strap across the ankle instead of being a slip-on.
Continuity mistake: In "The Ribos Operation", Romana stated that her age was 'nearly 140' (presumably Earth years, although this is never confirmed). However, in the later story "City of Death", Romana says that she is '125 years old'.
Delta and the Bannermen - S24-E3
Continuity mistake: Due to some sloppy editing of the "cliffhanger ending" at the end of episode 2, and again at the start of episode 3, the Doctor, Mel and Burton are seen to freeze in place for no apparent reason, just BEFORE we see the Bannermen line up and aim their guns at them.
Continuity mistake: The Doctor has his scarf when he first meets with the Vardans. When he returns to the TARDIS, it is on the coat rack.
Continuity mistake: In episode four, when the Doctor and Ian return to Frankenstein's lab, the monster is lying on the table in the opposite direction from when they left.
Continuity mistake: In episode five, the Doctor escapes from Global during the day. When Yates is caught it's dark, but the next scene, on the slag heap, is in daylight again.
Revenge of the Cybermen - S12-E5
Continuity mistake: At the end of "Genesis of the Daleks", the Doctor was wearing his big brown overcoat. However, at the beginning of this episode, he is wearing his red jacket again.
Continuity mistake: The TARDIS is missing its light the first time it's seen.
Continuity mistake: During Kroll's attack on the refinery, several pieces of the refinery get broken off and then reappear in subsequent shots.
Continuity mistake: In episode 2, when the Russian soldier is enticed into the water by the now-Haemovores Jean and Phyllis, watch his helmet, which he drops into the water as he moves towards them. When the camera angle changes to a shot of him from the front, we see his helmet slowly drift from directly behind him out to the right of screen. Then we cut to a shot of Jean and Phyllis, then back to the soldier - whereupon his helmet again drifts from directly behind him off to the right. Finally, when the other Haemovores drag him down into the water, look behind him and you'll see the helmet, sitting on the beach well above the waterline...
Continuity mistake: When Toos is being hunted by a robot, she shuts the door on its hand. When you see this scene from the inside of the room, the robot's hand is trapped at a different place to the next shot, which is from outside the room.
Underworld - S15-E5
Continuity mistake: When the Doctor races out of the R1C with the fission bombs in episode four, Leela follows, carrying a shield gun. She steps into the cave and is only holding her knife. Later, she has her shield gun back.
The Monster of Peladon - S11-E4
Continuity mistake: In episode six, the same extra is killed by both Azaxyr in the ambush and by Eckersley later on.
The Armageddon Factor - S16-E6
Continuity mistake: In episode 2, just after K-9 begins blasting the door, look behind Romana and notice that you can see the TARDIS - which supposedly left in the previous scene.
Continuity mistake: The Gatherer gleefully states that being on the roof is a fine of 500 talmars. Later, Cordo says it is 5 talmars.
Answer: TARDISes are generally available for properly authorised use on Gallifrey; they're not usually assigned to a particular Timelord on a long-term basis. The Doctor stole his when he left his homeworld.
Tailkinker ★