Nekoamon is the main antagonist of "Syobon '85", an update for Joke Day of "MARIO '85".
This is an evil entity similar to MX that resides in the Syobon Action game, it traps the soul of people inside the game to put it in the body of the main character so that it can kill it again and again for fun, although despite this He has a surprisingly friendly attitude towards his victims, being willing to talk and even play video games with them.
It is an entirely black anthro version of the cat Syobon.