At one point, Yasmin suggest Reversing the Polarity to fix a problem. This term was first used in the not-quite-authorized sequel to H.G. Wells' War of the Worlds, Edison's Conquest of Mars by Garrett P. Serviss in 1898. It became a Doctor Who (1963) staple beginning with the 3rd Doctor Jon Pertwee.
Kevin Eldon (Ribbons) played the companion Antimony in the animated miniseries Doctor Who: Death Comes to Time (2001).
Scenes with a creature called 'The Spindleman', which made an appearance in the cave, were filmed but later cut from the finished episode.
The two Norwegian characters, Hanne and Erik, are daughter and father. They have the same names as the daughter - father characters from the action film Hanna (2011), who are hiding from the CIA in rural Norway at the beginning of that film.