Revealing: When the robotic Doctor first appears - and in many of the later scenes involving the jungle on Mechanus - it 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.

Audio problem: Before the TARDIS materialises in the haunted house you can hear the Dalek's time machine sound effect for no apparent reason.

Visible crew/equipment: When the Doctor and Ian encounter the Frankenstein monster in episode four, you can see a Dalek behind them, even though it's long before the Daleks arrive in this time zone.

Continuity: 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.

Factual error: In episode one, Abraham Lincoln seems to have affected a southern accent and put on some weight.

Continuity: 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.

Visible crew/equipment: In episode four, when Ian and the Doctor descend the stairs into Frankenstein's lab, you can see a boom operator and mic behind them.

Visible crew/equipment: Near the end of episode five as the Daleks plan their attack, a BBC camera can be seen in the background on the left.