Your Elf's lil' coupon book

A binding contract that will work anytime of day,month,or year. No one can say no to a "Your Elf's lil' coupon book!

"Hey do u want to have a sleepover"
"no, it's a school night, I can't"

"Do u have a "your Elf's lil' coupon book"?"

"yeah,why?"
"use it! There's a coupon in it for a weekday sleepover!"