First, you have to talk to a Team Galactic person in Pastoria City. Next, you start to chase him around. After chasing him once, you'll have to battle your rival. Then the Team Galactic guy will give up and will battle you. Then, you will find Cynthia. She'll give you a Secret Potion for the Psyducks. Give it to them and then they'll get out headaches and will start to move away.
Complete the pokedex.
you get the National Dex.
You have to visit the battle tower thingy first, then they let you past
complete the sinnoh dex.hope this helps:)
You Have To Do A Lot Things And Beat Gym Leaders And At Some Point Cynthia Gives U Stardust And Asked U To Give Her Grandma A Necklace In Celestic Town U Use The Stardust On The Psyduck
Read this http://wiki.answers.com/Q/Where_is_the_5th_gym_leader_in_Pokemon_Diamond
Well first you need the secretpotion from Cynthia then you need HM Defog to be able to see once you get past the Psyduck
Complete the pokedex.
you get the National Dex.
You have to visit the battle tower thingy first, then they let you past
no because Route 16 is on Pokemon leafgreen and firered
you have to catch dialga on spear piller first
complete the sinnoh dex.hope this helps:)
You Have To Do A Lot Things And Beat Gym Leaders And At Some Point Cynthia Gives U Stardust And Asked U To Give Her Grandma A Necklace In Celestic Town U Use The Stardust On The Psyduck
they went away after i visited the resort area
you get a poder from someone you beet a gym or something and the this some sort of potion of cinthia and click a on the psyduck they should go away
There is, in fact, no route past route 24