Each Pokemon in the game has an index number that's completely separate from its Pokedex number, that's what the game uses to make them appear. Missingno appears when a number that doesn't have a proper Pokemon assigned to it is called. If you transfer these Missingno to GSC, you sometimes get a Johto Pokemon (so the index number 31 gives you Scizor for example). So maybe they'll do the same thing again. Although it's more likely that you'll just not be able to trade Missingno, it wouldn't be too hard to do a check for this.
