Marks the first appearance of the Time Lords' homeworld in the series, although it would be another five years before the planet was named.
In this initial appearance, the Time Lord culture (costumes, locations, technology, etc.) is very minimalist compared to the very detailed development to follow.
The uniforms worn by the Time Lords are the same as the one worn by the 8-year-old Master in the 2007 story, Last of the Time Lords (2007).
This episode is the first case of blank slating in the series: beginning with the next episode, the entire main cast is different with none of the regulars in this episode appearing. The only exception is Nicholas Courtney, who wasn't a regular during this story but had previously appeared and was yet to become a regular on the series.
The means of the time travellers' last-ditch attempt to escape from their Time Lord sentence was different in the original script. Rather than verbally duping the Time Lord into switching off the force field, the Doctor and Jamie took advantage of a weakening of the barrier near the floor to push Zoe through, enabling her to turn off the field.