The trials, tears and triumphs of five Mustang trainers on their way to Mustang Million will be featured in a new three-part miniseries on Nat Geo WILD. “Mustang Millionaire,” airing December 14, 21 and 28, 2013 at 10 p.m. EST, gives you a backstage pass to all the action from the adoption auctions to the sold-out Legends freestyle finals.