I'm blatantly ripping off RationalJenn with the title of this post... I trust she won't mind.
Via my wife, the following was uttered by my 3-year-old son today:
R: You know everything, mom! You're momniscient!*
Yes. Yes, she is.
* We often teach the kids $10 words, because they ask us what the words mean when we say something and they don't know it already. Omniscient came up recently, and R. took it and made it his own, in the context of his world.