Missingno. Questions?

Question

1. What is the chance of Missingno. appearing in the wild without cheating?
2. What can it do to your game?
3. Can you capture it?
4. Is there a way to prevent Missingno. from appearing ever?

Answer 1

• What is the chance of Missingno. appearing in the wild without cheating?
  If purposefully using a bug in the game counts as cheating, then then 0. Without doing the Old Man glitch, there is no way of finding Missingno.

However, if performing a glitch do not count as cheating, then Missingno. can be found fairly commonly on the line of ocean tiles along the east coast of Cinnabar Town in Red, Blue and Yellow. Its specific chance of appearing depends on your trainer name, and the rest lies in the coding of the game. It would be too hard to go any further than this since the result differs too much (this being a glitch and not something intentionally put in the game and all).

• What can it do to your game?
  Three things, two unfixable and the other fixable. Missingno. is surprisingly harmless contrary to popular belief.

1. If will mess up your Hall of Fame entries and turn them into glitchy nonsense. Many agree that this is nothing you should really care about, and personally I find it amusing. So unless Hall of Fame entries matter a lot you, then you shouldn't worry about this.
2. It will mess up the sprites of the Pokemon. Don't worry though, just look at the Pokedex entry for a legitimate Pokemon and it will fix itself.
3. It will multiply the item in the sixth slot of your bag. This is not a bad thing, and people catch Missingno. just to get an almost unlimited supply or Master Balls or Rare Candies.

• Can you capture it?
  Yes, definitely.

• Is there a way to prevent Missingno. from appearing ever?
  If you don't do this Old Man glitch, it will never appear. And doing the Old Man glitch unintentionally is basically impossible, so don't worry. The glitch only exists in Red, Blue and Yellow, so if you are playing a different game, Missingno. doesn't even exist.

More info

Comments

If you were to call yourself something normal, watch the old man's demonstration, fly to cinnibar island and surf in a specific place, a random pokemon depending on your name would appear.