Even if their mattresses are getting wider, the genre gulf between mainstream pop stars seems to be narrowing by the minute. Case in point, Rihanna and Jennifer Nettles' duet at the ACM (formerly CMA) Awards. The seemingly unlikely duo nailed Rihanna's hit "California King Bed" to an adoring crowd. Rihanna wore an appropriately tassled body-con shift, and Nettles kept things Pop Warner-banquet style in a purple and black pantsuit. Wondering what could've preempted the collab? Guessing it's not a high-paying Sealy posturepedic spokesmanship. More likely just that Rihanna's mundane metaphor about the very real girth of a California King mattress is so very country.