Zach didn't have a foot fetish. What he had instead was an inanimate fetish. He got turned on by just thinking about it.
Zach chose the footwear option. He selected reality shift, meaning he would slowly transform over the course of a day, but still be seen in that day as the footwear. He chose that the world would think he never existed until he transformed back. He decided to not put wearer awareness because he didn't want to freak Carlos out. His transformation time was set for a week, and maybe he'd set it for longer after the week was up.
The footwear option's description was "Become someone's footwear. Most people have so many different socks and so many different shoes that turning into one pear would mean you'd hardly get worn! Creating this option, we had in mind that you want to be worn so no matter what the wearer is wearing, you will instantly become it!"
After reading this he found a senses button. He wanted all five. He wasn't too big on the taste, but it was required with scent so he had to have it.
Finally, after choosing all of these options came the most important. Which to become, socks or shoes?