Pot belly pigs are "designer" pigs that were bred as household pets, they are supposed to get no larger than a medium dogs such as a lab. however a friend of mine had one that grew to be quite large, almost as large as a farm pig (which is where you get bacon from). Hers was about 160lbs.
Not in the US. If you have a pet pot-belly, be sure to offer only the recommended amount of food. Otherwise, the pig will eat more than is good for his/her health and get so heavy that the weight will cause VERY painful stress fractures in the bones of the legs.