S4, E14: Billy Callahan (guest star Colin Farrell) is a life-loving Irishman who comes to Sacred Heart Hospital after being injured in a bar fight and teaches Turk (Donald Faison) and J.D. (Zach Braff) a lesson about living life to its fullest. Meanwhile, Carla (Judy Reyes) and Elliot (Sarah Chalke) attempt to make social plans with each other but can't seem to stick with them, which creates tension between the two friends. Elsewhere, Dr. Cox (John C. McGinley) gets a vasectomy behind Jordan's (Christa Miller) back and is stunned by her reaction when she discovers the truth. Ken Jenkins and Neil Flynn also star.