We've already hit one of these in a major way. Leela. When I listened to Zagreus I had my first meeting with this companion, and it meant nothing. So I figured this Who run through would entail a big stop off with Four, like last year and Three. What better place to do that with Leela's hoping on board the TARDIS?
Leela's an odd one. I try to avoid most companion's until we reach a significant story for them. Or at least a decent one. She's one of two that I've messed that up with. The other is Nyssa, but The Mutant Phase did her quite a lot of justice. Yet when I heard Leela in Zagreus, and I was confused how this savage woman (I know that much) was on Gallifrey. Which pretty much spoils how her story goes. But that was all I got from it.
Here, I really like her so far. How straight forward she can be is quite a refreshing chance. When the Doctor starts his crazy explanations or hypothesising she just looks at him like he's mental. Yet at the same time she does rack up a bit of a body count. On the second the Doctor has to tell her to stop. It's kind of a surprise that she becomes a companion. Then again, I don't think the Doctor did have any intention of making her one. Leela follows and asks if she can come, and he gives her one more chance. A simple question “Why?” that if she answers correctly then maybe she might just have the right stuff. Instead she says the two of them get along. It's not enough. But Leela just runs in the TARDIS and hits a button, luckily for her the de-materialisation one, and that's it. The fact she invites herself along has quite endeared this new companion to me.
The rest of the story does just as well too. To start with the whole barbaric world believing in some weird mumbo jumbo felt pretty awful, but quickly you realise that they have some sci-fi stuff they have laying around and don't understand. It quickly escalated with the Doctor's “Evil one” moniker revealed as a mistake he made on a previously unseen journey. The crashed ship, generations split apart and sort of at war with each other, alternate words bastardised over time such as the tribes name of Severteem originally being Survey Team. It builds up into an awesome little universe. However, the Tesh's costumes and their bowing are utterly ridiculous.
But it's a minor thing, and overall it's a brilliant serial, and a great introduction to a new companion.