After defeating the first four gym leaders, follow the Galactic grunt that is in Pastoria City. After you chase him away, Cynthia will appear and she'll give you an item called the "Secret Potion". Then go to where you saw the Psyducks (not Golducks) and press A. After that, they will leave.
You can find Psyducks and Golducks in the Safari Zone
in box
At the end of the diamond and pearl series
Leave it with the nursery
leave 'em in the Pokemon daycare. they should have an egg
Just leave it alone for six hours. Be careful, because if you leave it for 24 hours or longer, the Pokemon will disappear.
Pokemon diamond
Pokemon diamond Pokemon diamond Pokemon diamond
talk to the fisherman in the building right when u leave jubilife.
Yes, leave 2 compatible Pokemon at the daycare in Solaceon town, (the more they like each other the better) and wait.
you cant be a Pokemon in Pokemon diamond
leave two banettes at the day care center and there will be a shuppet egg.