What if your pet grows and grows and grows ...

That is truly a large pig to be living in the house, but since they started with it as a small piglet, hopefully, it is house trained, and has good manners in the house. A pig is actually as smart as a dog is, so there is no reason that it could not be domesticated easily enough.
The reason it has grown so large is probably due to two factors.
The first one is that they bred a pot belly pig with a regular domestic breed that is normally grown for pork. The pot belly pig usually stays small, like they said this pig would do. However, a regular farm pig can easily grow to several hundred pounds before it finally quits growing.
The other factor is the food the pig is being fed. Regular pig food has growth hormones, and other additives so that the pig will put on weight as fast as possible, and grow as large as it can grow rapidly.

Pot belly pigs have to be fed a special ration, and then they will stay small, but not if they are crossed with a farm pig that is bred to grow into a large pig .