The CBS sitcom “B Positive” puts a new twist on the odd couple formula, starring Thomas Middleditch as a man in need of a kidney and Annaleigh Ashford as the acquaintance who, in a drunken gesture of generosity, offers to donate one of her own. He’s uptight and she’s the opposite. “She’s a wild child that needs to be tamed, and he gives her structure and helps her find her purpose in life,” ...