Certain Pokemon mates with every Pokemon (except MOST ledgendary
Fly to Canalve City,go down to root 218,put on max repel, go into grass and use poke radar. Keep going to shiny squares until you find a Pokemon called ditto. Catch him and he will mate with any of your Pokemon and give you male eggs (males have higher stats for some reason)- note: the egg will hatch into non-evolved version of Pokemon that ditto mated with, and may have some of it's extra moves e.g. HMs or TMs taught to mother/father pokemon
If you need more help, we've got more Pokemon Pearl cheats and also check out all of the answers for this game
Comments for this hint