How sweet is this: Superman star Henry Cavill was recently photographed at LAX with his dog Kal-El wearing a blue vest with the words: “Working. Do not pet. Emotional Support Dog.” And it’s also well-known that Ryan Gosling flies with his dog George, a registered Emotional Support Animal, or ESA.

Despite some of the bad press surrounding ESAs (did you hear about the woman who caused a stir by bringing her therapy kangaroo into a McDonald’s in Wisconsin?), as animal lovers, we know how strong that bond with our animals can be and that yes, being with our animal can calm us. And thanks to the U.S. Department of Transportation’s Air Carrier Access Act, ESAs, like traditional service dogs, are allowed in airline cabins. (By law, ESAs are also allowed in apartments that typically turn away pets.) The law does allow for common sense to prevail, however, so if you plan on taking a hyper goat or a 500-pound pig into the economy section on your next flight, the airline will probably turn you both away.

Though ESAs have been “on the books” for several years, more people today—not just celebrities—are signing their animals up as ESAs than ever before.

Here’s a closer look how ESAs differ from the typical service/therapy animals we’re used to seeing …