A woman and a kangaroo walk into a McDonald’s, and the woman says: “He’s my service kangaroo.”

No, it’s not the setup for a joke. But it may be a sign of the times.

In a culture that has increasingly embraced animals as an extension of family, the kangaroo incident has become part of a growing debate. With pigs flying — literally — aboard passenger flights, monkeys cruising the grocery aisles and large snakes hanging out in restaurants, the issue of what’s legitimately a service animal is getting murky.

“A lot of people don’t understand there’s a distinction between a therapy animal and a service animal,” said Dr. Rick Marrinson, a veterinarian in Longwood, Fla. “And because of that confusion, I worry that the people who abuse the law are ruining it for the people who really need it.”

In the kangaroo incident, which took place in Beaver Dam, Wis., in February, the restaurant called the police, who asked the woman to leave. But in August, when a man showed up at a Mexican restaurant in Nixa, Mo., with a boa constrictor wrapped around his neck — he said it helps him cope with depression — he was allowed to stay, even though many of the other patrons did not.

Elsewhere there have been parrots, ferrets and flying squirrels that allegedly disrupt panic attacks, alert their humans to impending seizures or allow people to overcome such disorders as agoraphobia.

When confronted by a “service monkey,” Transportation Security Administration officials at Orlando International Airport cleared it through security. (We’re presuming that they checked first to make sure it wasn’t carrying an oversized container of shampoo.)

The help these animals provide may — or may not — be real. But the debate they’re stirring up certainly is.

Two years ago, a campaign to crack down on phony service dogs, backed by groups that train canines, appealed to the U.S. Department of Justice to intervene. The proliferation of official-looking doggy vests bought online, the groups said, allowed badly behaving pooches to show up in restaurants, hotels and theme parks, hurting the public image of their legitimate counterparts.

The government didn’t bite. As long as the dogs weren’t biting, either, the folks at the Justice Department weren’t interested in getting caught in the middle of that argument.

Law leaves loopholes

Under the Americans with Disabilities Act (ADA), only dogs and, in some cases, miniature horses can be considered service animals, and those must perform specific tasks to aid people with disabilities — such as guiding the blind, alerting the hard of hearing, pulling a wheelchair, retrieving objects or interrupting impulsive or destructive behaviors.

But the law also says a business owner or employee can ask only two questions of a person accompanied by a service animal: Is it required because of a disability? And, what work or task has it been trained to perform?

The business can’t ask for any documentation, require that the animal demonstrate its service or ask about the nature of the person’s disability.

Further, there’s no universally recognized vest the animals wear or central agency to certify their training. And that, said Kevin Fritz, a Chicago attorney on ADA public accommodations, can make matters fuzzy.

“Every time an animal is deemed to have some health benefit, people become more imaginative in their claims,” he said. “And it becomes even more confusing, because individual states can have broader definitions than the federal law in allowing other species to be service animals.”

P.J. Suss, a 26-year-old Florida resident who breeds and sells snakes, fully supports tighter limits, even if it means leaving his snakes at home.

“The last thing we need is some idiot who brings a snake into a restaurant,” he said. “We have enough trouble with our public image.”

And as much as Suss enjoys watching TV with one of his more docile pythons in his lap, he doesn’t see snakes in a service role.

“I have customers who tell me their snakes are ‘just like a dog,’ but I don’t buy it,” he said. “Most of their brain is devoted to just surviving. You may be attached to them, but I don’t see them becoming emotionally connected to you.”

Therapy animals have rights

That’s not to say snakes — or other creatures — can’t provide comfort or emotional support. It just means they don’t have the same rights as service animals.

“Much of our relationship with animals is our projection anyway,” said Alan Beck, director of the Center for the Human-Animal Bond at Purdue University. “You believe that your golden retriever is listening to you, and you interpret this as love. We humans are social animals, and we need social support.”

Emotional-support animals — also called therapy animals or comfort animals — do have limited legal standing.

According to Pet Partners, a national nonprofit for owners of therapy animals, such pets must be prescribed by a licensed mental-health professional for a person with a mental illness and can accompany their owners in public areas only with permission from the facility’s owners or managers. But they can live in apartments, regardless of a “no pets” policy.

“Any animal has the potential to be therapeutic,” said Marrinson, the veterinarian. “From a neurochemical standpoint, attachment is attachment. When it comes to the neurological response of caring for another creature or getting some attention back, I’m not sure it matters if it’s a dog or a rat or an iguana. We love them.”