They whine at me and get a bit cranky, but that's all they do. :D Nefer and I often fight for who gets to sit on the office chair, which I win because I have thumbs and can spin the chair around until she gets off. But if I fail to install a Feline Thwarting Device such as a pillow on the seat when I get up for a break, she usually sneaks on.
Re: shoo them off