There are several. It's a bit mad, yeah? Rose can explain that, if you want her to.

[ She has such an expressive face. It's brilliant and totally charming. But she doesn't seem to understand humans very well yet. Martha wants to understand her better, too. But she has to stop herself from asking about the Avengers whether they're from the comic books. It would be rude, even if she's curious. ]

I'm from Earth. London, properly. I don't think I've heard of the Avengers, though. Are they friends of yours?