Mick is a boxer born with "Swimmer Puppy Syndrome." Basically, the muscles that pull his legs together were incredibly weak, leaving him flat on his stomach with his legs sprawled out to the sides. He was unable to walk, stand, or even sit.
Dogs born with Swimmer Puppy have a slew of health issues as a result of their condition, many of which make quality of life low and carry a very short life expectancy. Which is part of why Mick's story is so wonderful.
He was lucky enough to be taken in by the Mia Foundation and rehabilitated with pool training. They taped his legs in place and helped him develop the muscles he'd need so that he could learn to sit and stand. When he finally walked (and even ran a little), the Mia Foundation folks were there to capture the moments on camera. The footage has been set to the Rocky theme because, duh.
Get your tissues ready.