Fans may obsess over the chemistry between Dancing With the Stars couples, but the pros themselves are often the last to know who they’ll be twirling across the ballroom. From last-minute phone calls to specific requests from celebrity contestants, scroll below to read more about how DWTS matchmaking actually works: When Do 'DWTS' Pros Find Out If They're Returning for New Seasons? What We Know  The Pairings Can Change Up Until the Cast Announcement Cohost Alfonso Ribeiro pulled back the curtain on how fluid the casting process really is, telling Us exclusively in September...