There's more to humor than telling a joke and since Oliver is mostly non-verbal he tends to express his funny side using the tricks of physical comedy. But he does have one joke that I'd like to share:
Our favorite bedtime story is Green Eggs and Ham by Dr. Seuss. On almost every page there is a picture of Sam-I-Am holding a plate of, what else? Green eggs and ham. With every turn of the page Oliver takes great delight in drawing his hand back to his chest and then, with finger outstreatched, land arrow-like on the picture of the ham and say: "That's a fish!" with laughing eyes but a straight face. To this I respond in an outraged voice: "No! That's a HAM!" Sometimes we repeat this two or three times per page, growing increasingly loud and fast as we near the end of the book. Then finally, when the story is over and we turn to the inside back-cover, Oliver's finger poised over the picture, he says: "That's a. ..." then he lets his finger fly, stabbing the page and triumphantly calls out: "HAM!"