Series 5 of the sitcom begins with Ted (Josh Radnor) starting his new job as an architecture professor at Columbia University. Meanwhile, notorious commitment-phobes Barney (Neil Patrick Harris) and Robin (Cobie Smulders) begin dating, although neither of them know what they want out of a relationship; and Marshall (Jason Segel) and Lily (Alyson Hannigan) wonder if they should have a baby. Memorable guest stars include Jennifer Lopez and Carrie Underwood. Rachel Bilson has a small role as the roommate of Ted’s future wife.