You just keep catching them until you get one. It's relatively random.
Find a Pokemon that has serious nature, then walk up to this "guy" and if it asks you if you want to show him a Pokemon with a serious nature then click yes and choose the Pokemon you caught.
Any Pokemon can have a serious nature - you just have to catch one with a serious nature. You may have to catch a few before you find one. There is a 1 in 25 chance of a pokemon having a Serious nature as there are 24 other natures.
Pokemon don't have a nature from wat Pokemon it is. Do wat I do and keep catching easy 2 catch Pokemon till u find 1 wit a serious nature. There isn't a specific place with serious natured Pokemon
any Pokemon can have serious nature, just catch more Pokemon
any Pokemon could have a serious nature especially if you try breeding them until one with a serious nature shows up.
no you cannot make your Pokemon nature serious. You cannot change your Pokemon's nature. You simple have to find and catch a serious nature d Pokemon. sorry! WRONG! you can do that by using action replay game shark or any other cheating system for ds
If you are lucky and have good patience. Im pretty sure any pokemon can have it
Wingull, 'J' unown and Snubbull<----What crap! Thats the person's pokemon any pokemon can have a serious nature from Bulbasaur to Genesect! wat about a navi natured pokemon.
any Pokemon can have any nature!
its random, unless you have the Pokemon modifier
Pokemon are not limited to certain natures any Pokemon can have a serious nature, it just might take you a while to catch the one you want or breed until you get one
he means a serious NATURE