Revealing mistake: During the Doctor's early conversation with the Time Lord, there is fog swirling around them. When the Doctor agrees to take on the mission, it suddenly appears very concentrated around the tip of the rocks behind them, as if generated from a source behind the rocks. Normal fog would not do this, and it's clear that dry ice was used as the fog effect (DVD commentary confirms this). (00:02:45)Daz
Continuity mistake: In episode three, Eckersley turns on the security monitor. The very first image is of the entrance to the refinery, but it does not show the Doctor and Gebek trying to break in. Eckersley then flips through the images and finds one of the refinery with the Doctor and Gebek breaking in.
Audio problem: When the Doctor arrives at UNIT HQ in his stolen car, he speaks to a guard. We see close ups of the guard twice...but watch the brief clip of the Doctor (Jon Pertwee) between the two and you can just see that his lips aren't moving even remotely in synch with the words. (In fact, it is just a repeat of the previous shot of the Doctor, with new lines dubbed in).
Factual error: The Doctor states that the radio waves take two minutes to get from Mars to Earth. The time interval can vary dramatically depending on where the two planets are in their orbit. But at absolute closest approach, Mars is just over three light minutes from Earth.
Continuity mistake: When the Count's henchmen come into the café to get the Doctor, Romana and Duggan, they usher them all out at gunpoint. When you see them in the location filming in Paris, Duggan's not there...but back at the Count's place (in the studio in London) he's reappeared.
Revealing mistake: The Daleks that appear in this and other Doctor Who stories were rather expensive, so some ingenuity was required to make the small number available look like they were more than they were. Tricks employed in "The Power of the Daleks" included making four Daleks look like an army by having them circle around the set a few times (note the delay between the fourth Dalek exiting and the "fifth" Dalek entering), and the blatant use of photographic blow-ups in place of "real" Daleks.
Revealing mistake: During the fight scene between Toberman and the Cybercontroller, the Cybercontroller uses a very visible harness to lift Toberman over his head, and the wires attached to the harness Toberman is wearing are also very visible. When Toberman, in return, lifts the Cybercontroller above HIS head, it is obvious that what Toberman is lifting is an empty costume, with no-one inside it.
Revealing mistake: When the robotic Doctor first appears - and in many of the later scenes involving the jungle on Mechanus - it is very obviously not William Hartnell playing him, but a vaguely similar double. In addition, his lines have been dubbed by Hartnell and do not always match the movements of his mouth.
Continuity mistake: At the beginning of the third episode, the countdown reads 49:18:32 in the close up, but when the Brigadier walks across the room it now is on 49:15:01. (In other words three minutes thirty one seconds have elapsed). Yet these two events are about ten seconds apart. Also, the timer should never read either of these times. The professor moved the countdown forward to exactly 49 hours (49:00:00).
Continuity mistake: In episode 1, when the Doctor and Leela leave the TARDIS, the door is open and is not moving. They then walk away from the TARDIS for a few seconds. When they hear the attack on Bullard (the Cab Driver) and run past the TARDIS again, the door is magically closed.
Revealing mistake: 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."Daz