NCFCA currently has 2 main categories designed to be funny. Humorous Interpretation, and After Dinner Speaking. A platform, and an interp. There's a third speech type, however, that has no specifically funny version: Limited Prep. So, I suggest the category of Humorous Impromptu. The name could be different - perhaps Stand-Up, or Impromptu Comedy - but the idea is as follows:

The category could be fantastic to help people practice creating jokes on the fly. NCFCA is for practicing speaking skills, so why not the skill of being funny without something being prepared ahead of time? We have categories that help people practice humor (ADS, Humorous) and categories that help people speak on the fly (Impromptu, Apologetics, Extemporaneous), but nothing designed for both. That's where this category comes in.

Now, I'd like to look at some likely criticisms of this topic, and respond to them.
1. Just make your Impromptus funny. I have two main responses, the first being: Just make your Informatives funny. If there's no distinction between a category geared towards funny speeches, and one geared towards more serious speeches, why separate Informative from ADS? There is a difference, just as much as there is a difference between Informative and Persuasive, despite the lack of rule differences. My second response is: Optimized for humor. You see, Impromptu as a category is not optimized for humor. The topics aren't always topics you can make jokes about well. However, simpler topics that allow for more creativity in humor could help optimize the category for being funny. Additionally, giving a bit of extra prep time would also help optimize the category for humor - you might want a little extra time to think of jokes.
2. Too hard. I've heard people suggest that this category could be too hard, and it would be difficult to think of jokes. I have 2 main responses: Firstly, the response of: Improve over time. Impromptu is also quite difficult, but through doing more and more Impromptu speeches, people get better and better at their delivery. In here, people would get better and better with their jokes. My second response is that it improves people's skills. The purpose of NCFCA is not to be a competition that makes people do everything they can to improve their chances of breaking, the purpose of NCFCA is to help people improve their communication skills. Even someone who's really bad at speaking benefits from NCFCA. Similarly, even if this category proves to be very difficult - which I doubt - it will still help people improve their speaking skills.