This is the ZZAZZ glitch. It can be done without Gameshark or Cheating device, but there isn't much point because it will ruin your save game and your Pokemon. I have lost my save many times trying this trick. It is called the ZZAZZ trick because it changes your name to something such as ZZAZZ, but in this example it is much longer. It is caused by facing a glitch trainer when doing the Ditto Trick (Mew Trick), this one was Special 252.
It has many effects, see the video for some of them.