Why isn't this kid sleeping

Because my husband is nice, I got to see a movie this afternoon. Role Models, a must see for anyone who likes comedy laced with foul language and inappropriate innuendo. When I got home around 7pm Monsieur Henry was asleep, dinner was made (just needed to be reheated), and it looked like we were going to have a nice, quiet evening together. Then Henry woke up. First it was a diaper change, then play time with mom and pops on their bed (where Henry was extraordinarily cute and giggly), followed by a late-night snack (well, late night for him anyway), and finally back into bed (baby-babbling sounds keep issuing from his room). Why isn't this kid sleeping?