For example, if you'd been having a conversation about Topic A, then later Topic B, and there was a joke involving a double meaning of a word that relates to both A and B. Wrap that up in a one-liner, put it on a Google Glass, and a decent number of people could deliver it well enough to get a laugh.
The idea that GPT is going to make you funny is a bit like thinking you could be John Lennon if GPT would teach you how to play guitar.
GPT might help you pass off some bit of wit in an email, but any art it creates (comedy is art) is going to be circumscribed by its inability to be truly creative rather than merely copy/regurgitate existing material. And the reason art is hard is because people are extremely perceptive about what is actually creative/funny/surprising. You can’t fake it.
Will it have a good hit rate? Surely not at first, but of course it will get better over time. And just like with graphic arts, much of the value is that it can create lots of options, and you can choose to just use the ones you like best. It's like a wacky brainstormer that is sometimes right-on (or inspires you to create something that you never would have thought of).
"I'll get back to you assuming I remember where my head is tonight!"