>>19378761Just google it, it's not like I came up with it. It's pretty simple.
1. Put two magikarps in the daycare, IV's don't matter, make sure one of them is japanese or the kind the ditto you have, also if you want HA make the female have HA
2. Get out of the DC, save game
3. Ride till the guy turns back with an egg
4. Get egg
5. Ride till it hatches
6. If it's shiny, do not save the game (important), close the game without saving, backup the file. You now have a shiny seed. Start the game again, switch parents in the daycare center for the pokemon you want to hatch shiny, get the egg, hatch, it's shiny. It will have the same IV spread and ability (ha or non-ha) as the karp you hatched previously. So if the karps were both 6IV and the random stat was for example speed and you ended up with 5IV and speed IV at 16 then your shiny will also be that.
7. If it hatches non-shiny reject the next egg if the guy is turned around already, save game, repeat steps from 3.