J.D.'s a daddy, but will he ever grow up himself? Elizabeth Banks (The 40-Year-Old Virgin) guest stars as Dr. Kim Briggs, J.D.'s baby's mama. But there's trouble in the nest, and someone's going to fly. Can J.D.'s brother Dan (Tom Cavanagh, Ed) pull him out of his childish funk? Even more surprises are in the works, including a 'green' episode with an eco-conscious message; you'll never guess who names himself the EO (Environmental Officer) of Sacred Heart. And, a softer side to Dr. Cox? Also, say an early goodbye to a surprise staffer. All this and an unforgettable contest to be Sacred Heart's No. 1 doctor — it's not just going to be competitive, it'll be downright dirty.