I have been asked to teach a few things for newbies at work, without coding background.
I used the metaphore of pizza, empty pizzabox and no box for teaching NULL. I have read it here on Devrant, written by someone awesome of the community here.
My boss overheard me explaining it, and said that that was the most beautifull expanation of NULL he ever heard.
.......I was like: yaaay Devrant FTW!

Also newbies understood it instantly so kudos to you sir, original poster!