Doctor Who: Terror of the Zygons

Terror of the Zygons was the episode that introduced the Zygons into the Doctor Who universe. The Zygons, of course, returned in the 50th anniversary special, The Day of the Doctor. The episode has the Zygons as beings whose planet has been destroyed, and thus refugees. The episode thus offers opportunity to discuss real life post-colonial and post-disaster situations, and what the rights of refugees and of others are.

The episode also addresses environmental issues, as the Doctor comments on human dependence on oil, which he refers to as a “mineral sludge.”

The supernatural is present, in the references of locals in Scotland to evil spirits haunting the moors.

Human religion is also present, as the Doctor is able to refrain from breathing, and put a spell on Sarah to do the same, using a method he learned from a Tibetan monk.

The episode also offers one of two explanations for the existence of the Loch Ness Monster (the other occurring later in the episode Timelash).