This brings me in a round-about way to today's writing prompt. Because it's about jokes, but not in the way that you think.
What’s your favorite joke? Write it down.
Don’t analyze why it’s funny. That’ll guarantee it stops being funny. Instead, focus on why it’s your favorite. Why was this the joke you picked? What is about this joke that appealed to you? When did you first hear it? Has it stuck with you for years or was it the most recent joke you heard, so it was first in your mind?