In this Sweet Sixteen story Mary Kate and Ashley are put to the test when they swap places with their best friends. The number 1 brand for tweenage girls, Mary Kate and Ashley are once again entertaining girls in their latest Sweet Sixteen series. But can the girls deal with the changes and without each otherWhat would happen if your best friend became your sister Mary-Kate and Ashley are about to find out when their friends, Brittany and Melanie challenge the sisters to spend a week in their shoes. Babies are cute, but can Mary-Kate handle the responsibilities of having a little brother, dirty diapers and allAshley is thrilled to hang out with Melanie's supercool fashion-designer dad, but she's about to find out just how strange daily life without her sister can be.