Princess Serena noticed that her slave was not as clean as she wanted her slave to be. She had to make him clean as it was not negotiable. She used her dirty sneakers and her smelly socks to punish him. She humiliated him by choking him using the socks and making him lick the soles of her dirty sneakers. She humiliated him and she made him realize he had no option but to up his cleanliness standards.