I’ve always liked that Rose does not just jump into the role of a time-traveler lightly. It’s an adventure at first, an impulsive choice, but the second episode of the reboot really shows the effects of that choice. She’s overwhelmed by everything, the myriad alien races all coming in at once, the TARDIS getting inside her head, psychic paper, and the end of the world 5 billion years into the future. While there, of course something goes terribly wrong and the Doctor must save the day.
It’s not a terribly complex episode, but it’s supposed to establish the Doctor and Rose together. Rather, the fact that they need each other. She needs him to watch out for her, while she needs to keep him human. He thinks it’s a lark, seeing the end of the world, while it deeply impacts her, as it’s her home planet about to be obliterated. He’s been deeply wounded by the last great Time War, and he’s a bit too reckless. He doesn’t think before he acts, while she keeps him grounded in humanity.
Also, there is a bit of not-so-subtle commentary on plastic surgery and appearance. Cassandra, the last surviving human, has continually altered her physical appearance to the point that she is little more than a stretched piece of skin with a face on it. Not only is she hardly human, physically, but she also epitomizes human nature: “5 billion years and it still comes down to money.” It doesn’t matter that the earth is about to disintegrate, someone will always be looking for a way to exploit others.
Characters introduced who we’ll meet again: Cassandra and the Face of Boe (in his present and past forms!).
“I’d rather die than live like you–a bitchy trampoline”
“Moisturize me, moisturize me!”