Question about my cat?

These things in themselves do not sound like a problem. My cat once sneezed about a gazillion times in a row in the middle of the night and of course we thought she was deathly ill, but she was absolutely fine. No nasal discharge or anything. My younger cat frequently claws at the wall and yowls while looking up at the ceiling and there is absolutely nothing there! I volunteer at a cat shelter and have seen all kinds of strange behaviour. I think all cats are slightly bipolar. :)