Njexus originated on the forums of a popular wrestling gossip website, they are the opposite of trolls, in that they post really, really nice things on peoples threads/videos. Sterotypically, they are Irish-Canadian and have elaborate forum signatures.
Poster 1: "So then I say that my horse has no facial hair."
Poster 2: "ROFL! OMG MAN! THIS IS AWESOME! YOU ARE THE BEST!"
Poster 3: "Dude, you are so a member of the Njexus."
Yoop is slang for youtube poop, a term which here means "An awful/terrible video placed on youtube for the destruction of other people's brains."
Grammatically speaking, perhaps there should be an apostrophe somewhere in Yoop, but according to several religions, if an apostrophe were to be placed in the word "Yoop" the solar system would go out of alignment.
"Today it is Friday, and Saturday comes afterward..."