The so-called "Puppy Bus" is already a viral sensation, and we got its founders to break down all the tricks and treats behind their suddenly booming dog walking/training service.
Mo and Lee Thompson joined "TMZ Live" to talk all about their biz, "Mo Mountain Mutts" ... after their dog bus unexpectedly became a social media phenomenon.
The husband/wife duo told us the bus is just one part of a day filled with dog training and dog walking around Skagway, Alaska -- and after those incredibly calm bus rides, the pups get out for an adventure, full of exercise and socializing.
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They say the outings are planned to be physically and mentally engaging for their 4-legged clients ... like challenging hikes or a beach run.
The Thompsons admit their popular bus videos are the product of carefully choosing which pups have enough obedience training to go to their assigned seats without causing a ruckus. They added that the dogs' personalities, ages and manners are also factors.
As for how it all started ... Mo says at first she was just walking friends' dogs during work breaks, and then she started doing biking and hiking trips with 'em.
Six years later, it's evolved into a full-blown biz ... with a very popular bus!!!