(WASHINGTON) -- They're leaving town -- and for millions of their adoring fans -- you could call it, well, unbearable. After more than two decades of "panda diplomacy," Washington's popular pandas were being returned to China Wednesday. The Smithsonian National Zoo's three current pandas, Mei Xiang (May-SHONG) Tian Tian (tee-YEN tee-YEN) and Xiao Qi Ji