Our family friend, Jim, used to have 2 potbelly pigs named Tinkerbell and Rosie. They were extremely cute, and they were potty trained...they rang a bell next to the door to go outside. They were very protective of Jim and their house. Loved to get scratched and rubbed.

Many people don't know this, but pigs are smarter than dogs!!

Also, if you plan to keep the pig in the house, it is wise to get a potbelly instead of a farm pig. Farm pigs can get up to 600 pounds, and have to be housed outside. Potbellies are around 30-60 pounds or so, and can be housed inside.

Considering A Potbellied Pig As A Pet?
Is A Pig Right For You?
Right Pet For You?
A Pot Belly Pig Info Page: Diet, Health, ETC.
Potbelly Pig FAQ Page

Hope those links are helpful to you.

P.S. What about a miniature horse or small pony?