Piglet, Miniature Pig

Miniature pigs, also known as teacup pigs, are sometimes kept as pets and gained a measure of faddish popularity, although they grow to be quite large. They are frequently sold as small piglets and exaggeratedly described by breeders as having an adult size not much larger than a puppy. However, these pigs in fact grow to the size of a Labrador Retriever and are not, by any means, "tiny". Infrequently, pigs are purposefully fed less food by breeders to keep a diminutive size in order to appeal more to the buyer. These malnourished pigs often have a very short lifespan, or may skyrocket in size once given enough food, much to the owner's surprise.
Other notable references
A Yucatan miniature pig is the unofficial mascot of the Animal Rescue League of Boston.