So my sister has a tabby cat who we got when he was 3 years old and now is almost 7. He is a nice cat and is social and even sometimes cuddles up with me even though he is technically my sisters cat. However whenever I have some friends over, he’ll growl, hiss and there was even a time he bit one of my friends. There have been other times where he chases my friends and even stalked one of my friends. My friends and I don’t always go up to him, he’s the one who instigates everything. I end up having to put him in my sisters room and lock him in there cause I don’t want him terrorizing my friends. Now he doesn’t do this with every single one of my friends but with other friends he does. Is there anything I can do to stop him from terrorizing my friends?? I just don’t want to keep having to lock him up as it does tick me off when he acts all crazy and such