Even if it is a galaxy, it doesn't necessarily mean it's their galaxy. It could be the next closest one. Galaxies do collide once in a great while, so it very well could be about to happen there in a few hundred million years or so, and in the meantime they're getting closer and closer.

(then again, I suddenly realized I don't know how the size of an oncoming galaxy would appear differently from one side of your own to another... I wonder if being on the opposite side would make enough of a difference for us to not see it during the rest of the saga... hmmm)

But I agree it doesn't really matter. Just throwing out another possible explanation. I'd be very surprised if that background was changed.

And by the way, you've got mud on your knees.