Princess Bride Q: ROUS scene

This scene always bothered me: Buttercup falls into the lightning sand and Westley jumps in to rescue her. After he pulls them both out, they are holding each other and Westley looks directly at one (or two?) ROUS’s. Immediately following this as they are continuing through the swamp, Westley says, “Rodents Of Unusual Size? I don’t think they exist.” and then of course is attacked by one as he finishes the sentence.

Why did he say that immediately after he clearly just looked directly at one?

He didn’t want to scare her.
Or, he was being ironic.

And it allows the screenwriter/director to introduce the ROUS without a lot of character discussion.

He was trying to keep her spirits up. Right before that he was telling her with forced cheer how simple it would be now to avoid the fire bursts and lightning sand.

It has been a while since I have seen the movie. I remember the audience sees one before the attack but do the characters?

As Bosstone observes, he’s just being reassuring in the sometimes panglossian way that a good guy is obligated to be when the lady that he cares about is feeling anxious. They have just barely escaped a horrible death in the lightning sand, but even that is spun into reassurance: “You were clever enough to discover what it looks like, so in the future we can avoid that, too.”

It’s a nice metaphor for something that isn’t that uncommon in relationships. For example, my nervous-by-nature wife frets quite a bit about what will happen with our finances when our second kid arrives and she switches over into stay-at-home mode. Now, realistically I know that making it work is going to involve a combination of extra work and some sacrifice and that it will be difficult at times, but in conversation on this subject, I don’t let any of my own (perfectly natural) trepidation show. “Nah, look - I’ve just had a generous raise, we’ll save on daycare, there’s no limit to the amount of overtime I can put in, yadda yadda yadda.”

When you have some necessary obstacle to overcome, you do everything you can to get through it, and try to keep the people you love as easy-in-their-mind about it as you can.

In the book, selective presentation or even substitution of reported fact is an even more explicit leitmotif than it is in the movie.

Yes, Westley has just seen two of them, and it’s clear that he’s uneasy about it. I think he may even gently and discreetly guide Buttercup away from them, being careful not to let her know that they’re there.