My response would have been wayyyyy different, but that's probably why this kid is the spelling bee champ and I'm not. His maturity level well surpasses mine. I would have gladly used it in a sentence. "What kind of numbnut chooses 'Numnah' as a spelling word!?!?" I would have used it in the plural version too, because, let's face it, saying "numbnuts" makes me giggle. Like seven year old making his armpit fart. Bwahahahaha.
BTW, This was just yesterday, at the national spelling bee.