ABC has given Castle an order for one additional episode, bringing its fourth season to 23 episodes. The quirky detective drama starring Nathan Fillion has been a slow builder but was able to branch out of an early cult status to become a solid performer in the Monday 10 PM slot. Besides the first season, which launched in midseason, all seasons of Castle have been supersized. Season 2 and 3 consisted of 24 episodes each. Word is one more is all ABC needed this season. The network’s flagship series, comedy Modern Family, already has an order for 24 episodes.