19-year-old tennis star Sloane Stephens became a Brent-Musburger-style overnight sensation when she upset Serena Williams at the Australian Open, gaining almost 40,000 Twitter followers in one night and earning <a href="http://blogs.wsj.com/speakeasy/2013/01/23/sloane-stephens-aces-twitter-after-beating-serena-williams/" target="_blank">congratulatory tweets from Shaq, Dirk Nowitzki, singer John Legend and more</a>.