One of the great myths of autism: people with autism understand things very literally, and therefore do not "get" jokes, especially jokes involving puns or other non-literal language.
Joey has had a very difficult time with knock-knock jokes. After all, knock-knock jokes require punning.
Why are you crying?
Blue is my favorite color.
Yes, the literal side of things shines through. Uncle Lou, famous in my family for his jokes, even did his best to get the point across when we visited at the holidays, to no avail. I think it really hit my family that Joey really is different when they couldn't get him to understand a joke. Fortunately, I bet Uncle Lou will keep trying, because it is clear that Joey understands that you are trying to make a joke, and that jokes are supposed to be funny. He just can't figure out how they work- and the faces he makes are precious.
I was in Andy's room, reading our bedtime stories, and generally trying to convince the little guy that he was, indeed, sleepy and needed to be rested for school in the morning. I had just gotten him tucked in, and snuggled in (Andy likes to be snuggled to sleep. Oh, gosh, darn. ;) ), when here comes Joey.
Joey hops into the bed, sticks his feet on my tummy, and giggles, "I defeated* you!" and leaves.