When I was in high school we had a cat that was, shall we say, not small. My cousin was staying the night (taking my bedroom) saw the cat laying on her mat. She said "Wow, your cat is really fat". Claws and teeth suddenly displayed with much hissing. it was quite a fast reaction. I grabbed the cat before any harm could be done.

That night as I sat on the couch reading, the cat walked past with that "I am going to do some damage" crouch. Walked into my room (where she never really went at night), and proceeded to "play" on top my cousin. Retrieved cat was still pretty ticked.