Here is how i think cankles began. Enjoy!

 One morning, skinny Joe was walking down the street when he discovered a magical donut factory and twinkie shop that had been abandoned. He walked inside, and what did he discover? A world of treats and sweets ready to eat! He ate and ate, and soon skinny Joe was now Big (if you know what I mean by big) JOe. And grew a cankle. the end.