To Catch Aceus you need to use a action reply cheat that gives you a azure Flute or you can buy it as a Nintendo event if you use the code for action reply go to the pokemart and talk to the green guy and he will give you the azure flute either way once you have it go to the spear pillar which is in mt coronet and it will say do you want play the azure flute selec yes and a staircase will open and there is aceus at level 80.
Dialga
i know you can catch a ditto
luck
pee wee Herman
you need a action replay
go to the mansion garden
You can't catch Palkia in Pokemon Diamond, you'll have to trade with Pokemon Pearl
Go to serebii.net for all your Pokemon needs
aftewr you get your national pokedex you will get a place where you can catch it only of you have the bayleaf on Ruby.
I think by talking to dawn lil' sis'
No you can't you can catch it noly in pokemon dimond pearl or platinum
Its ACEUS