Cardboard cutout Daleks are used in a number of scenes to give a sense of numbers. These are given away by their base-supports and flat appearance.
After the Doctor and Ian are taken to the Dalek spaceship, a member of the production team can be heard cueing the entrance of another group of prisoners.
Some of the Dalek dialogue was pre-recorded and played into the studio during filming. During the first scene inside the cell, the tape is miscued and the word "All" is heard with no Daleks present. The next line of Dalek dialogue begins with the word "All", but it does not occur until three minutes after the miscue, thus revealing the miscue.
When the Doctor and Ian use "magnetism" to obtain the iron bar from inside the box in the Dalek cell, a slender rod can be seen pushing the iron bar out of the box.
After the end of a seen with the Daleks it goes to the cell where The Doctor and Ian are held but at the start of the shot the word "all" in a Dalek voice is heard which is meant for the next Dalek scene.
When the Doctor and Ian are discussing the Daleks' appearance, a crew member is visible over the Doctor's right shoulder before hurrying out of shot.