EXCLUSIVE: NBC’s freshman Chicago Fire has been a late bloomer. The firefighter drama did not premiere until October. It started off slow but held onto its lead-in and did just well enough in its first few airings to earn a back 9 order. The Dick Wolf-produced series then kept steady and started to grow, hitting series highs earlier this month. Now it has been given an order for one extra episode, bringing its freshman season to 23 episodes.