- Alternate Character Interpretation: Cessair of Diplos is, on the face of it, an alien criminal who happens to be in posession of the third segment of the Key to Time, disguised as the Great Seal of Diplos and will stop at nothing to prevent the Doctor from obtaining it. But the story hints that there's more than this than meets the eye: is she an agent of the Black Guardian who is trying to stop the Doctor getting the segment on the Guardian's behalf? Maybe, but a third explanation arises from "The Armageddon Factor": Cessair was a false agent of the Black Guardian. She was given the task of stealing the Great Seal, supposedly to stop the Doctor getting his hands on it, but actually to help him. The Guardian's plan was to trick the Doctor into giving him the complete Key. By this reasoning, Cessair stole the Great Seal, and was actually doing what would have been the dirty work. End result: the Doctor has the relatively easy job of recovering the Seal from a criminal as opposed to stealing it from its proper home on Diplos. Cessair got turned to stone for her efforts. The Doctor was then able to seek the remaining segments.
- Big-Lipped Alligator Moment: Near the end of Part 3, the Ogri attack a pair of random campers to recharge themselves. This has no bearing on the plot, beyond giving the Professor and K9 a temporary reprieve before Cessair returns.
- Les Yay: There is a definite, if subtle, romantic undertone to Rumford and Fay's relationship. Mary Tamm herself said "We were all so innocent back then" when the Les Yay was pointed out to her.
- Magnificent Bastard: Cessair of Diplos. She absconded with part of the Key to Time and three Ogri, which she used as attack "dogs". With the ship hauling her to prison stuck in hyperspace by Earth, she passed herself off as a deity among the locals. For ages they fed her Ogri (with animal blood once human sacrifice was abolished), and she bought up the land her shrine was on, through the ages. Oh, and she may have been an agent of the Black Guardian.
YMMV / Doctor Who S16 E3 "The Stones of Blood"