Your sidekick is loyal. Clever. A great comfort to you and others. But does that mean your animal companion deserves access in public places that other people's pets don't get?
Maybe. The law is murky and the answer depends heavily on your animal's skills, your frailties and your conscience.
The good news for your furry friend is that over the last few decades, legions of people and institutions worldwide have awakened to the many ways animals can help people, even without elaborate training. So now governments and businesses increasingly sort companion animals into several categories.
The greatest latitude is given to the trained service dogs that can help people cope with blindness, Parkinson's and other challenges. But many hospitals, nursing homes and schools now also welcome therapy animals, which receive less training but nevertheless offer comfort and distraction when volunteer owners bring them around.
On a typical Southern California weekday, you may find Gordon, a 173-pound Newfoundland dog, strolling the halls of Children's Hospital Los Angeles. A 25-pound cat named Tank pays similar visits through a charity called Love on 4 Paws.
In Malibu, five miniature horses (about 28 inches high at the shoulder) stand ready to comfort sick and traumatized children and adults through Gentle Carousel, a Florida-based charity.
But there's another creature category, and it has started many an argument in recent years: the emotional support animal (ESA). These animals usually don't have elaborate training or ties to an institution. But they are credited with calming their owners, who take them into public spaces where conventional pets may be banned or limited.
Numbers on companion animals of all kinds are hard to come by, but a JetBlue spokesman said more than 25,000 of its passengers boarded with animals in the first 11 months of 2014. That was 11% more than all of 2013.
According to airlines, hotels and government agencies, many pet owners are describing their animals as ESAs. Some carry letters from licensed health professionals attesting that they suffer mental or psychological disabilities that are eased when their pets are present. This, said Lisa Lange, Los Angeles-based senior vice president for People for the Ethical Treatment of Animals, "is a sign of how people regard animals today. They see them more as individuals or family members."
Some who work with animals, however, see the ESA situation as a growing problem because of the pet owners who fib about their infirmities (or stretch the truth) to get their pets better access. "It's not right," said Nikki Reagan of Pacific Palisades, who is known in local hospitals as the owner of Tank the therapy cat. Animals can do wonders for people, Reagan said, but too many pet owners are gaming the system.
Several companies sell ESA evaluations, letters, registration cards and other accessories on the Web, sometimes requiring telephone interviews, sometimes operating on the honor system. But there is no federally recognized registry for any kind of companion animals (service, therapy or emotional support), so consumers should expect no guarantees from these vendors.
In fact, federal laws are conflicted when it comes to ESAs. Some, including the landmark Americans With Disabilities Act, give no extra privileges to people with ESAs. Yet other federal laws do, which is why airlines see so many furry fliers.
The public can call the federally funded Pacific ADA Center in Oakland (www.adapacific.org;  949-4232) for guidance on how the laws affect them and their animals. But here are some general guidelines for travelers:
Service dogs are generally permitted in any public place that safety allows.
Therapy dogs get no particular perks outside the schools and hospitals where they work, except for miniature horses.
At Amtrak and the Los Angeles Metropolitan Transportation Authority (Metro), ESAs are treated like conventional pets. That means they're banned on Amtrak except for certain routes in Illinois. On Metro trains and buses, they're permitted in carriers so long as they don't require their own seat.
The federal Air Carrier Access Act, on the other hand, allows ESAs to fly in the passenger cabin on commercial flights at no extra charge, usually on the passenger's lap or in a carrier under the seat. The federal Fair Housing Act permits ESAs in condos or apartments that ban pets. That law doesn't cover hotels, but many upscale lodgings accept ESAs, including some that ban conventional pets.
As for the Americans With Disabilities Act, the U.S. Justice Department decided in 2011 that it should apply only to disabled people accompanied by service dogs and, "where reasonable," miniature horses.
But under the ADA, businesses can ask only two questions when trying to determine whether an animal is truly a service dog: Is it required because of a disability? What work or task has it been trained to perform?
Facing such complexity, many businesses have decided to just say yes to ESAs.
Given all that, said Kate Buhrmaster, project leader for the therapy dog program at Children's Hospital Los Angeles, she's not surprised by what she sees as a proliferation of dogs bearing ESA credentials.
Still, she added, "We tell all our volunteers that their dogs have no special privileges outside of the hospital."
Debbie Garcia-Bengochea, a former middle-school principal who now is educational director of Gentle Carousel, takes a similar approach with her organization's 24 miniature horses, which typically weigh about 70 pounds.
The horses do most of their traveling by land. But when air travel is necessary, Garcia-Bengochea said, they don't fly on commercial aircraft. "They hitch rides with private pilot planes," she said.