I know it sounds stupid but missingno IS in showdown if you wanted to test it. It’s not a very good Pokémon but it does have actual stats and everything! I think I know the answer but it’s worth a shot…
Edit: even pokemater agreed there should be a Missingno page (it’s not a msq but still)
Yeah I'm going to say no, even though I know you'd all enjoy it.
It has no relevance to competitive Pokemon and I'd rather not open the can of worms around CAP/fakemons and such.