ER (NBC) Returns Thursday, April 10 at 10 p.m. So Far This Season: The long-running medical drama passed the 300-episode mark with the usual mix of high-octane medical cases, office politics -- including the naming of an interim chief (guest star Kari Matchett) to the chagrin of Pratt (Mekhi Phifer) and others -- and personal dramas, focusing heavily on Abby (Maura Tierney) and her estrangement from Luka (Goran Visnjic). When It Returns: Former "Sopranos" star Aida Turturro is reportedly signed for a guest arc as a patient. And whatever happens this spring, it likely won't be the end: The show is reportedly close to returning for a 15th season.Mekhi Phifer of 'ER.' Photo courtesy of NBC.