It sounds like they might be hiding something.........insecurity; who knows. Tell them not to try so hard. And also try to get them to relax and maybe take on more profound subject material. Good luck.
If you can excuse yourself, it might be best as everyone has very different sense of humor. my grown daughter and I have VERY different senses of humor, so unless you have to be with this person, I would just say " I have to go"