What?

Today I walked down into the living room to join Julia while we ate sandwiches for lunch.  As I came down the few steps towards the couch I looked down and started laughing at this:

I don't see what you're laughing at...

Julia's reply to my laughing was, "what?", as she didn't think anything was really out of the ordinary.  I didn't really know what to say.  Oh well, whatever works!