The Sontarans' probic vents, previously seen to be the size and shape of a button, become thin slots in this serial, convieniently large enough for Leela's knife to enter.
Plot Hole: The Doctor tells Borusa that the Great Key is kept in the hands of the Chancellor to keep it secret from the President. This sounds fine, except that in The Deadly Assassin, it was clear that a Chancellor could later become President (as Borusa eventually does).
Stor: I am Commander Stor, of the Sontaran Special Space Service.
The Doctor: The S.S.S.S.… Isn't that carrying the alliteration a little far?