I'm not sure which word you mean. Could you check the spelling? If someone is a little cookie, then that person is cute. This is not a common usage. If someone is a little kooky, then that person is strange. If someone is a little cocky, then that person is arrogant and egotistic.

I think what you mean to say is that "Someone is a little cocky". Cocky can mean arrogant or self assured. Usually has a negative conotation and is of course colloquial.

You can look up "kook", kooky just means "like a kook"

If one is "kooky" then they are strange or eccentric. This term is not always negative. Sometimes "kooky" people contribute positively to society because they do see things a bit differently.