Pikablu was a name for Marill before its official release. Marill can be found in many places in Pokemon games of the metal (G/S/C) series and later. The Pokemon mentioned in this cheat, however, does not exist. There are people who have hacked the flash memory of their games to try to obtain every possible Pokemon, even those that don't exist and show up only as "???" when you battle. Until they discover something of this sort, don't assume it exists. Oh, and your game cannot tell if you've GameSharked. Otherwise, there'd have been anti-GS measures way before now. Well, if you GameShark something obvously impossible... but otherwise, no.
