One of our cat's kittens is VERY different from the other 3. (They are about 6 weeks old) She is very fat, and all the other ones are skinny. She was born that big....she was either the last kitten born or the second last. She VERY rarely plays with the other kittens, usually she sleeps or lays and looks around. She hardly ever walks, we brought them outside yesterday for the first time and she just like, she slowly waddles around, she barely went anywhere. When you look into her eyes, you see something very different from looking into another kittens eyes, I can't really explain it...At first I thought she was blind...I moved my hand back and forth on front of her to make sure. I don't know what is wrong with her...yesterday she looked like she needed to use the litterbox so i put her in it. She just sat with her butt in the litter, and her front paws hanging over the edge, and closed her eyes as if she was falling asleep, like it was too much of an effort to do anything. My dad keeps saying "There's something not right about that kitten." Anybody have any suggestions? Is she just fat and lazy? Or could there be a mental problem with her?