The Doctor's "half a dozen times" line, mentioned below. Subtle reference to the War Doctor? Simply not counting "The Five Doctors?" Or is it just rounding?
Has the Doctor never mentioned Sarah Jane before? Or is Rose just being catty?
Continuity Lockout: There is no mention of the events of "K-9 and Company", which might leave some viewers confused as to why Sarah has K9 Mark III in her possession considering that K9 Mark I and II only travelled with Leela and Romana (and later Adric) respectively. Ironically, this was the result of a BBC edict that was designed to prevent Continuity Lockout for newer viewers, with Russell T. Davies having been told not to explicitly reference the events of any pre-2005 stories.
Harsher in Hindsight: When Sarah Jane mentions that the Doctor has regenerated, he says he's done it "half a dozen times" since he last saw her. At the time the episode was broadcast, it was taken to mean that the last time he saw her was when she left the Fourth Doctor in "The Hand of Fear", which people considered odd, given that she met his fifth incarnation in "The Five Doctors". Following the revealof the War Doctorduring the show's 50th anniversary, that line takes a whole new meaning.
Sarah Jane telling the Doctor he needs a Smith on board. Guess who was cast next...
Ho Yay: Mr. Finch softly asking the Doctor to rule the universe at his side to a background of piano music comes to mind.
Les Yay: A fair amount of this between Rose and Sarah Jane, once they iron out their differences. Particuarly in the final scene, where they give each other a decidedly heartfelt embrace and Sarah tells Rose to "Come find me" after Rose stops traveling with the Doctor.
Narm: Every time Anthony Stewart Head starts screeching like a bat to summon the rest of the Krillitanes, especially considering his subtle and sinister performance up to then. On the other hand, can you think of any actor who could do that without looking a little silly?
The episode tries to play up Rose as being disrespectful towards Sarah Jane by bringing up how the Doctor has never mentioned her beforehand, but it comes across more as sassing back after Sarah Jane had just made a shot at Rose's youth, before they are properly introduced to boot.
While Sarah Jane's initial clashes with Rose can sometimes make her look less sympathetic than intended, Rose also has moments where she accidentally looks like the one in the wrong. Namely, she seems to have thought that she's the only one who's ever travelled with the Doctor in 900 years, and that any other companions are automatically competition. This is especially apparent when compared this to other companions from different eras meeting in "The Five Doctors" and "The Two Doctors". Companions like Martha and Donna, and Yaz and Jack being on friendly terms when they meet later in the Revival Series only amplifies how much Rose stands out; this is the only instance where a companion feels threatened by another.