Not Meowth
Cat, are you drilling?
Apparently, there's a site that explains the wonders of Missing No. 'M, and the other one. I think it was if you have a Y in the 5th place in your name, you'll get 'M, and so forth. Not sure, though :\
You might be thinking of the thing where during the Missingno glitch on R/B, while surfing up and down Seafoam Island random Pokémon will appear, and what kind they are depends on the letters in your name.
For instance, as Mike, I got an abundance of Kingler and Starmie.