A woman with a crying baby in her arms bearing down on the luxuriously empty seat next to you used to be every airline passenger’s worst nightmare. That was before pigs started flying.

A college professor and US Airways passenger, Jonathan Skolnik was alarmed late last year when, on a flight out of Connecticut’s Bradley International Airport, his putative seatmate bustled her way down the aisle carrying a moving duffel bag that, upon closer inspection, turned out to be a potbellied pig.

Nonchalantly tying the pig to the armrest with its leash, the owner set about stowing her belongings in the overhead compartment. “Oh my Lord,” Mr. Skolnik, who doesn’t really come across as an animal lover, emailed, “where is she going to put that animal. I am burying my face in my sweater to hide from the stench. . . . Now I, who dreads a dog coming too close, am contemplating an hour next to a big pig on the lap of my fellow [passenger].”

I happen to find pigs intelligent and attractive creatures and even had a pet pig as a child (he was named Runt, and, sadly, he never gave me the time of day, but that’s another story). Even so, I would look askance at what the pig did next: it pooped in the aisle. This story had a happy ending, however, at least for Mr. Skolnik and other non-agrarian types on the flight: ordered off the plane (but not before her little piggy had cried wee wee wee all the way up and down the aisle), the woman finally hoisted her beast over her shoulder and beat a defiant retreat. The plane erupted in applause from relieved passengers.

What was a pig doing on an airplane? It seems that the pig had been claimed as an “emotional support animal”—an E.S.A. If you haven’t yet flown with a pig, count yourself lucky. More and more “emotional support animals” are taking to the skies. They not only fly but fly for free but in the owner’s lap instead of being confined to a kennel that must fit under the seat in front of the owner, the fate of mere pets. Animal-dependent people are making their presence felt on the ground as well. “Lunch was ruined because Ivana Trump sat next to us with her dog which she even let climb to the table. I told her no dogs allowed but she lied that hers was a service dog,” an online review of a fancy New York restaurant stated. A man in Missouri recently claimed the boa constrictor draped around his neck at a restaurant was his service animal, helping him cope with depression.

In legal terms, service animals are genuine professionals and have undergone extensive training to learn how to provide much-needed assistance to a human being with an identifiable handicap. They are the patient seeing-eye dogs sitting at the feet of their owners, ready to do what is necessary to enrich the life of a human being. An emotional support animal, on the other hand, is along for the ride, so to speak, just to make its owner feel better. Their status entitles them to no special treatment beyond public transportation and in housing that is off limits to mere pets. It can’t be stressed too firmly that this is the extent of their legal privileges. But few people know this.

Theoretically, people who just want special privileges for their pets can be asked to show a letter certifying that animal solace is necessary for their wellbeing. It is supposed to be from a health professional and include the code number for a condition listed in the DSM (Diagnostic and Statistical Manuel of Mental Disorders). However, it is easy to go online and buy an official looking document “registering” a pet as an E.S.A. (you can also order a cute little “service animal” vest). “You could register a Beanie Baby, as long as you send a check,” Patricia Marx admits in a celebrated New Yorker piece about her efforts to take an alleged emotional support animal to places it had no business being.

Armed with fake certification, Ms. Marx took a turtle to lunch at E.A.T. in Manhattan where Turtle (also his name) hydrated in a dish of water, brought by a thoughtful waiter, while Ms. Marx enjoyed the borscht. “Why did the turkey cross the road? To get to the Hampton Jitney,” is the way Ms Marx introduces Henry, a turkey with whom she not only rode on the jitney but also dined in a deli. She also flew to Boston with a pig named Daphne, a far better traveler than the previous pig. All in all, Marx, with relative ease, took five alleged E.S.A.’s to places they ought never to have been admitted. While inspecting the nineteenth century treasures at Olana, a New York State Historical Site, Ms. Marx’s alpaca troublingly held its tail aloft, which is alpaca for “I gotta go now.” (It didn’t.)

The New Yorker story trafficked in absurdities to make a point that applies to less exotic situations. I am an animal sop, but even I recognize that there are places they don’t belong. Right now I have a lovely young relative who wants to bring her dog to a wedding, a guest apparently unwelcome by the bride and her family, even though it has been declared an E.S.A. (by a real doctor, I hope). I’m with the bride. Dear Niece, you will learn as much and more about coping if you leave the pet behind and show up and act like a normal wedding guest. A pet can teach its owner a lot about love and responsibility, but treating pets as E.S.A.’s and taking them where they are—legitimately—not wanted is an exercise in selfishness or exhibitionism.

If you can’t go without the pet, don’t go. It is a sign of the decline of civility and the obligation to be pleasant to others that people with mild or feigned emotional maladjustments hold the rest of us over a barrel because of these alleged problems, which, frankly, are theirs to handle without becoming a public nuisance. Moreover, the increasing popularity of E.S.A.’s is making life harder for people who genuinely need service animals. It is also making it harder for their trusty animals.

People with unnecessary E.S.A.’s are like able-bodied people who obtain disability payments, thereby threatening the solvency of the system for people who are actually disabled. They are also making life difficult for the service animals that have a real job to do. Jody Ambrose, an animal behaviorist who has traveled with service dogs told the BBC, “These dogs are not machines and one of the hardest things in the world for them is when they are solicited by another dog to play or to fight.”

And here’s a final thought: animals, as a rule, don’t like to fly. Take it from me. The very worst journey of my life was flying with my cat Bede from New York to DC., a necessary trip for which Bede had a ticket. When the TSA official noticed that my ID had expired, she took one look at the kennel, from which bloodcurdling sounds were coming, and hissed, “Run. Run fast. Get on that plane.” The Incorrigible Bede kept it up throughout the flight, making everybody in our vicinity miserable and leaving me to think wistfully of the traveling conditions of the Donner Party.