Knock, knock, G*d's there.
G*d came to me in a dream and here's the joke that She told me
G*d: knock knock
Me: Who's there?.
G*d: I am.
Me: I am who?
G*d: I am who I am. <laughter ensues>
In case you don't get the joke: "I am who I am" is Exodus 3:14. When Moses asks "Who are you" that's the answer. It is sometimes translated as "I am that I am"
This is why G*d (and I) thought the joke was funny.
Do you think it's funnier now that I have explained it?
I guess you had to be there.
In the dream, G*d said She liked "who I am" better, plus, bonus, "it fits the knock-knock joke schema."
Or maybe I just made that up.
Me: That's what she said. <snicker, snicker>