First, train a Mareep in Gold or Silver to level 15 and evolve it into Flaaffy, then train the Flaaffy to level 30 and evolve it into Ampharos, and then train the Ampharos to level 100. Then give it Rare candies until it becomes level 0 and then go to the move deleter and delete all of its moves except Thunder wave. Then, trade it to the Crystal version. There, teach it a damaging attack and train it to level 5. Then, delete the damaging attack and trade it to the Yellow version (the nurse won't stop you). When it is in Yellow, it will be a Dratini!