Do ya consider MissingNo to be a villain?

I don't. It gave Trainers infinite of the 6th item in their bag(Like Master Balls!) in R/B.
MissingNo took a break during G/S/C, letting the "Glitch kids" (3TRAINERPOKE, LM4, and others) mess things up, but returned in R/S, giving Trainers a chance to catch Celebi. Then in Emerald, our good friend, MissingNo showed up at the Battle Tower in the P.C. box, allowing cloning of Pokemon and items being held. Leave the evil to Team Rocket, MissingNo's cousin 'M, and the "Glitch kids".