Some time in the past few decades, owning a pig as a pet stopped being completely out-of-the-ordinary.

You might not own a pig or know anyone who does, but you’ve probably heard of people doing it. And the kinds of pigs that are associated with pet ownership come with specific kinds of names: mini-pig, micropig, apartment pig and teacup pig are just a few. Then there are the horror stories that circulate about people getting a pet pig only to have it grow into a full-sized farm animal.

Here’s the thing: they’re all full-sized farm animals. The idea of a manageably sized pig goes back a few decades, writes Jake Swearingen for Modern Farmer, but it is and always was a marketing scam.

The incredible inconvenience of having a hard-to-train, growing pig in the house forces many people to give the hogs up, he writes. Rescue operations seek to rehome them or give them sanctuary, but it’s a big job.

Mini-pigs are only mini in comparison with domestic farm pigs, writes Rachel Virginia for The Dodo. “So-called teacups are actually potbellied pigs who are either underfed to stunt their growth or who are sold under false pretenses,” a pig rescue expert told her.

Potbellied pigs still reach 100-150 pounds, she writes, and trying to keep them as pets is bad for both sides of the bargain. Many breeders tell new owners to underfeed pigs so they’ll stay small, writes Swearingen, and they don’t have thousands of years of domestication as pets behind them. Although pigs are notoriously smart and exhibit a great deal of social behavior with other pigs, they don’t naturally take to being human pets, and they get lonely without other pigs around, Virginia writes.

Like the animals, the problem of mini-pigs isn’t small, wrote Marissa Curnutte for National Geographic in 2014. The number of porkers in the United States and Canada being kept as pets had risen to “perhaps as many as a million” at that time, she wrote.

Potbellied pigs came to the United States from Canada in 1986, she wrote. American zoos received a few dozen Vietnamese potbellied pigs and private breeders began working with that breed and other relatively small pig breeds to create smaller and smaller pigs.

The strategies breeders used included inbreeding and underfeeding the pigs, she writes. And in the murky, unregulated world of pet pig breeding, even some commercial hogs were sold as pets. These animals often met grim ends or headed to already overburdened sanctuaries when their owners stopped being able to care for them.

The American Mini Pig Association, a breeders association created to oversee the mini-pig industrial complex, had recently formed when Virginia was writing. It's helped to define the mini-pig term and has also launched a petition against misleading names.

In 2015, Smithsonian reported that a Chinese firm responsible for producing genetically altered tiny pigs for use as lab animals was planning to sell them as pets. No word on that yet.