Last year I acquired a kitten from a friend. Said cat was born September 17th (so she's nearly a year old now, I got her at 10-11 weeks of age). She's a dilute calico, short-hair. Her entire litter was born with SEVERE fever coat (I had only ever seen fever coat in black cats/primarily black cats, but this litter only had one primarily black male kitten, the rest were one male brown tabby, one female standard calico, one female torbie, and two female dilute calicos. They all looked ashy grey-white with slightly darker heads. Three kittens were born with regular tails and three kittens (the torbie, standard calico and one of the dilute calicos) had irregular, kinked tails. The torbie and standard calico had shorter than average tails, one with a kink at the base and one with a kink at the tip. The dilute calico (my cat) had/has a kink mid-way through the tail. Anyways, her name is Pecan. She was the runt of the litter and the last to learn how to walk- she dragged her hind legs at first and while she's able to run, walk, jump and climb just fine now her gait is a little odd and her hind legs seem a bit longer than 'normal' and angled out. She looks a bit bow-legged, really. She was a very affectionate, playful, amusing kitten. She's still very very playful and can be quite amusing and has her moments of affection but she's very aggressive. I have a very difficult time trimming her claws (she squawks at me, bites me very hard, jerks her head around while she's biting me, kicks me, etc.) and I can't brush her because she'll attack the brush and fight it/bite it. A few months ago she started getting more aggressive to the other two cats we have (both sixteen year old females). What started out as annoying kitten-play toward them turned into stalking, staring, intimidation, swatting/herding, etc. Our short-hair calico Artemis has developed toileting issues because Pecan will attack/stalk Artemis while she's in the cat box. I don't think Artemis has used the cat box for over a month, she's been going in the bathroom in the tub and on the floor if there's clothing/a mat/towel to go on. Even then, if Pecan sees her go into the tub she'll wait at the edge and 'trap' Artemis in the tub and won't back down until I or another person living here physically removes her from the bathroom. Artemis has basically become a cupboard cat- she never, ever leaves the bathroom cupboard unless she needs to toilet or if the door is closed and Pecan isn't able to get to her. She attacks and bullies our medium-hair tortoiseshell Callisto as well, however Callisto is a very docile, patient, submissive cat and was 'under' Artemis in 'ranks' so to speak, so she hasn't gone down in 'rank' with Pecan being introduced. If anything, it seems like she's gone up in 'rank', since Artemis has been basically reduced to an anxious hermit that has to be fed and watered IN the cupboard. (She won't eat or drink if it's outside of the cupboard, even if it's in the bathroom on the floor nearby.) Artemis will even urinate in the cupboard if she feels she can't get out and go safely in the tub. Pecan also is not receptive to being taught not to do things. She does a great many 'naughty' behaviors and rather than learning from being relocated/deterred, she continues to attempt to do them. After a time she gets frustrated by my persistence and will bite/attack me and it hurts. I've installed multi-cat feliway pheromone plug-ins and have gotten pheromone collars. Artemis and Callisto like them, they' sniff as if very interested, will rub their cheeks/lips on them, etc. If I offer it to Pecan to sniff, she squints and rears her head back and will run away if I try to offer it again. I'm not sure what to do. I'm reluctant to take her in to see if she needs medication but she does strike me as neurologically different and her aggression/intimidation/etc. is getting worse, it seems. While amusing, she does a strange behavior (and she's done it since she was very small) where she'll be be playing and suddenly kick herself in the head or face with her back foot, then proceed to attack/bite her leg/foot. It's funny, but it's also bizarre and a bit concerning at times. Any thoughts, comments, concerns, recommendations, advise? I am not going to rehome my senior cats and I am very reluctant to rehome Pecan. I met her before she was old enough to leave her mother (I want to say four or five weeks old) and she 'chose' me- crawled into my lap and fell asleep and stayed in my lap for two hours. She's also my first OWN cat, as these senior cats are family cats we got when I was a small child. As a footnote, before I forget, all cats are spayed. Seniors were spayed at about 6-7 months of age, and Pecan was spayed about that age as well.