You must have a cheat called "Pokemon Modifier"
The man in the green suit comes only when you activate a Pokemon mystery event (for example if you own Pokemon battle revolution for the wii you can buy things and send them via mystery event to your ds. The green man will then give you whatever you bought.)
In Pokemon Diamond Pearl and Platinum, a man in a green suit can be found in the Pokemarts. He is not in any specific city. He is just in every Pokemart.
There is no cheat you can only battle him once!
it depends which man
you need Pokemon ranger you need to do the mission on ranger to get the egg then you need 2 ds/i then transfer the egg to diamond or the Pokemon game you want then you get it like an event in the game you go to pokemart with one gap in your party and talk to the green suited man the you get don't forget to save when you got it
get mystrey gift go to resort area every day until you see a man with a green hat
In Pokemon Diamond/Pearl, you find a old man at route 212 with a Leafeon.
You can't trade Pokemon between Pokemon Diamond/Pearl and Leaf Green/ Fire Red, although you can migrate Pokemon from Leaf Green/ Fire Red to Pokemon Diamond/Pearl using Pal Park, which is in Route 221. (Available after deafeating the Elite Four and Champion).You don't trade, you simply Export from Fire Red and Pokemon, once on Diamond/Pearl can not be sent back to the original game. First insert Fire Red into the GBA slot on your Nintedo Ds, at the main menu for Diamond/Peal choose Import Pokemon, you will be asked to pick six Pokemon, (Pokemon with hm's can't be transfered btw) after choosing your six continue the game on diamond and go to the Pal Park on route 221, talk to the man at the counter he will let you in to catch the Pokemon that were transfered over, Don't worry the park balls are like master balls and will always catch the Pokemon on the first try. Once you have caught all the Pokemon time will be up and you will leave when you are done tell the man at the counter to transfer Pokemon to the PC, save and boom you have Your Firered Pokemon on Diamond/Pearl. This also works the same with Emerald, Ruby, Sapphire, and leaf green.
go into any pokemart and talk to a green man and he will give it to you. Make sure you have a space left in your party though.
Eterna City I think
The Pokemon Is happiny
The Apricot Man (Kurt) is only in Johto. Sorry. :(