It was a game, and, as we know, learning through games is spontaneous and natural. There is a wide range of speech patterns within the single genre of joke. Jokes are common to all cultures. Jokes embody a culture. Speech behavior that is learned by listening to, and telling jokes can be generalized to speech acts other than the joke.
Jokes are funny.
They relax the tension in the classroom. What is needed in a classroom is a reaction that is real because it is spontaneous. This is where jokes and funny stories can come in handy. They lower the affective filter and create a relaxed atmosphere in the class. Most jokes are short so it does not demand long periods of attention while listening.