Fillerbunny's understanding of friendships and relationships was very simple. If someone treated you nicely, and you had some things in common, then it was natural that you should like each other. As for marriage, it was something that people did when they really liked each other, and as for sex ... well, he had no concept of that at all.

He probably would have found it horrifying, in fact.

So while the subtleties of what River said went rather far above his little rabbity head, River's happiness was certainly not even slightly in doubt, and he was very happy for her in turn. "Oh, that is very good. I hope I get to know him better. I guess I will, since you're getting married and all."