Madame Madison did not like the food her slave had prepared. She wanted him to learn to cook better meals and as a result, she rode him like a pony. That was his punishment and his motivation to do better. She even whipped him when he did not do it the way she wanted or when he got tired. She also got him to lick the soles of her boots.
This guy thought he could lie to mistress Gaia and her friend and get away with it. They realized what he had done and they punished him painfully. They did not do what he expected them to do. They stripped him naked, whipped him and rode him like a human pony. The mistresses nearly broke his back as they rode him together at the same time. Not even his cries of pain were enough to get him off the hook.
Lady Karame wanted this guy to learn to respect her. She did not feel like he respected her enough. So she forced respect and fear by turning the guy into a human pony. He had no choice but to carry her around as well as to endure her whipping. He understood that if he was to avoid such punishment, he had to learn to respect her so he did it.
Mistress Sveta had never ridden a pony before and she was dying to. She could not get one in her house so she turned her slave into one. She had fun making the slave carry her around the house. She would whip the slave painfully when she felt that he did not do what she wanted or that he was slow. It was painful for the slave but fun for her.
Mistress Gaia and her friend Vivienne wanted to add mistresses to their group. They held auditions and a lot of people applied. They narrowed down to two and they humiliated them to find out whether they would take the punishment and humiliation. They pony play trained them and rode them like human ponies. The mistresses endure the pain and humiliated and they were accepted into the group with open arms. They now belonged there.
This slave was not meeting mistress Sheena's expectations of him and she was pissed. She had to teach him a lesson and she forced him to do as she wanted. To signal how serious she was, the mistress forced the loser to be her human pony and she rode him in the house. She even whipped him when he got tired and that got him going again. It was brutal.