now you know

neener and nener are two different things.

i discovered that neener is actually the "correct" way to spell it, in so far as my friends and I have used it.

nener can be used in place of "niner", such as for 9. that is what nener-nener can mean, it is like saying niner-niner.

neener is more of the interjection, usually rude or out of place, used to annoy.

"i just don't know what to do, it feels like--"

"NEENER"

source: urban dictionary again.