Let's see, in real life? Uhh doorframes mostly. I've literally cracked more than one doorframe by turning too quick. More RECENTLY there's this one tall bookshelf that I keep almost bowling over with my butt because I have to try to squeeze through the door without opening it all the way so Soggy doesn't try to run out to where the other cats are...

I've also sat in a chair and the arms broke off to either side