because some people might be a little curious about why this glitch occurs, im here to cure your curiousity. the game uses a random number generator, in which you use it to get into certain battles. there couuld very well be a glitch like this for eveery pokemon. apparently, in an earlier version of the game (obviously pre-release), they used the rng as a "backup" to get any pokemon, and never erased it from the games database (because if they do that pokemon wont exist). i would say that there is something like this for every single pokemon. snorlax's and pidgey's are identical to missingno's. for more "in-depth" info pm me.