Ticklish cat?

My roommate had a cat like this... she was so cute and loved when anyone pet her. She would then roll over on her back, and logically I umed she wanted me to rub her belly. No, it was just a ploy to attack my hand!! Haha. I think she did it on purpose to get her kicks. My black cat will usually let me pet her on the belly, but if she is in a bad mood she will kick me with her back legs to let me know I should stop. My other two love attention and usually don't object to being pet on their bellies. I read somewhere that when cats fight, their belly is the most vulnerable spot and they try to protect it, so that's probably why some cats are skittish about it.