Mary-Kate and Ashley are swapping places with their best friends, but will they cope?
What would happen is 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 have a little brother, dirty diapers and all?
Ashley 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.