Sadly I lost all three of my Norwegian Notched Rats a little while back, but let me tell you, they had to be the best and smartest pets I've ever had. They could swim around the bath tub, walk a tight rope, snuggle, sit on my shoulders with their ferret harnesses and leashes, and they never bit anyone (except my ex-husband - but everything wants to bite him)
I still have my little man though. Shamus is a 2 year old miniature Dachshund, red in color, and a complete guard dog. He made the pit bull across the street retreat the other day, but I don't think it was because she was scared - I think she was laughing too hard to even think about attacking. He has a girlfriend too. My mother has a 14 year old mutt, Poopie Bear (Don't ask - I never did - I was afraid too) that he loves to distraction and even though he's fixed he still tries to consummate his love for her every chance he gets. If he can't get a hold of Poopie Bear my youngest daughter's huge stuffed frog will do. It's really funny to watch him snuggle under it, grab it by the leg with his teeth and take off with it flopping around on his back down the hall. The damn thing is about 4 times his size. My daughter's given up trying to keep it away from him.
My girls have a long hair black and white tuxedo cat that they've appropriately named Munchkin. She stopped growing when she was about 6 months old, so she's pretty small. She's also a pain in the ass.