As Derek stood waiting, a 16yo boy walked in. He walked up to Derek and explained that he needed some sneakers, in a size 8. Derek explained no problem, take your shoes off and slip these socks on. The boy complied and slipped them both on, then sat down on the bench and pulled out his phone.
Derek walked around the corner, but he kept an eye on the boy. Out of the corner of his eye, he watched as the boy's feet slowly began to expand, sliding further out on the carpet. They were now an inch longer than his previous shoes, and still growing! Derek laughed giddily at the thought.
Because the socks were so big, they were also having an effect on the boy's legs, though Derek didn't notice this part. As the boy was playing on his phone, his legs grew just a couple inches longer, and gained more hair on them. The growth was nothing compared to his feet however, which now measured around a Size 13! They extended a full two inches longer than his feet previously. And they were still growing, steadily expanding across the carpet.
Derek loved watching the expansion, and he just kept watching. The feet on the boy looked ridiculous! Looking at the boy's old shoe, Derek saw that the feet were clearly much bigger than the shoe. He realized that they had finally stopped growing as well. Walking back up the boy, he asked to remeasure. Sliding the boot in, he held his breath... Size 18. The boy had Size 18 feet, 10 sizes bigger than what he walked in with.
Shaking with happiness, Derek quickly retrieved Size 18 sneakers and gave them to the boy. He bought them instantly with no try on, tossed the socks off and walked out barefoot. Apparently the socks made you like being barefoot.