ChatGPT appears to only know around 25 jokes, and can't make a coherent original one when asked to.
I have often asked it to produce a joke when demonstrating it for friends, and the results have only included one of the 25 jokes here. You can easily make it produce an original joke by specifying something that should be part of the joke, like writing “Please create an original joke involving a radiator and a bicycle”.
I just did this, and the reply was: “Why did the bicycle get in trouble with the radiator?
Because it kept wheely-ing close and telling hot air jokes!”
I think it is a decent attempt that would have taxed a human being too.
But most of its jokes are in the form of riddles, and I therefore also often have asked it to produce jokes that are in anecdotal forms.
One such result was:
A man walks into a doctor's office with a carrot stuck in his ear. The doctor takes a look and says, "Well, I can see the problem. You have a carrot stuck in your ear!" The man replies, "I know that! Can you please help me get it out?" The doctor takes a deep breath and says, "Alright, I have an idea. But you're not going to like it." The man asks, "What is it?" The doctor responds, "Well, first, I'm going to stick this banana in your other ear. Then, I'm going to tell you to jump up and down on one foot while flapping your arms like a chicken." The man looks at the doctor incredulously and asks, "What kind of crazy idea is that?" The doctor shrugs and says, "Hey, it may not work, but at least you'll look like a complete idiot while you're doing it!"
This is certainly not a great result, but being a decidedly uncreative person myself, I can accept it for the effort.