Mistress Lisa was disappointed at her boyfriend and to make sure that he learned not to piss her off, she made him a human pony and she dominated him like never before. He did not want to lose her so he did what she wanted and that is how he ended up being used as a human pony. He had to carry her until he could not do it anymore.
Mistress Irina and her friend mistress Lera chose to use their pony play fetish to pass time as they were bored at home. The mistresses did not have much else to do and that was why they had to make sure they had a great time with pony play. They even whipped him when he did not cooperate with them and that was the most painful thing they did to him as his balls were not spared.