The reprise from the first episode differs slightly, the Dalek Sucker arm that menaces Barbra is larger and thicker than the one seen at the end of the previous episode.
Just before the Doctor, Susan, and Ian are escorted into the cell (just after the camera has panned across from Barbara to the cell door), an off-screen voice can be faintly but coherently heard calling out the cue "stop".
Early in the episode, when Ian, Susan and the Doctor are talking in a corridor, the shadow of a boom mic can be seen on Ian's face.