One way to get 999 rare candies in Pokemon Platinum without purchasing any cheating devices would be to use the Battle Tower cloning glitch in Pokemon Emerald and then migrating the rare candies attached to a Pokemon to Pokemon Platinum. This process can be very tedious and time consuming since the player first needs to clone a rare candy along with a Pokemon on Emerald version, and then migrate the rare candies attached to Pokemon at a maximum of six Pokemon per migration to Platinum. The transfer is also a one-way deal, meaning that any Pokemon transferred to Platinum from Emerald version can no longer be returned to Emerald.
To be able to clone a Pokemon along with any other item in Pokemon Emerald, the player must first defeat the Elite Four to gain access to the Battle Frontier. Once the player gains access, the cloning glitch in the Battle Tower can be exploited, allowing the player to clone as many rare candies as desired when attached to a Pokemon he or she wants to clone.
After cloning the rare candies, the player must then proceed to Pal Park where Professor Oak has invited him or her and save. The option to transfer Pokemon will then be available to the player once Pokemon Emerald is in the Game Boy Advance slot of the Nintendo DS and Pokemon Platinum is in the DS slot. All Pokemon that are migrated from Emerald along with attached items will be at the Pal Park on Platinum with a 100 percent catch rate.