If you mean "how can I get Johto Pokemon into Pokemon Emerald", then you can do that by either catching them in-game (as far as I remember) after completing the main Pokedex.
The three Johto starters can be obtained once you complete (catch) all Pokemon in the regional Pokedex. You can also transfer their second (or third-) stage evolutions from Pokemon Colosseum via GameBoy Advance-Nintendo GameCube link cable. You need to finish the story in Colosseum for this to work, however.
If you mean "how can I transfer Pokemon from HeartGold/SoulSilver/Gold/Silver/Crystal to Emerald", put simply, you can't. Sorry.
You get one Johto starter in Emerald for completing the Hoenn Pokedex. You can trade them into FireRed. Unfortunately, Croconaws (along with Totodiles) cannot be caught in Pokemon FireRed. You must have one traded to you from Emerald.
Basically, -just- and I use the term loosely, obtain all Pokemon obtainable in Emerald/ruby/sapphire, on such games, then choose a johto starter (Birch will call you) and trade. Only way, sorry.
You have to complete your Hoenn Pokedex. After you get the diploma go to a PC at and youll find a Johto pass. Go on the Ferry and they'll take you to the Johto region. I don't know if this works; I haven't tried it yet. My friend told me it ONLY works for Emerald.
It's possible yeah.
In Pokemon Emerald, it's impossible to leave the Hoenn Region. The Kanto, Johto, and Sinnoh Regions are inaccessible in Emerald. Sorry.
you trade with others who has the kanto, johto, or other hoen regions
No, you need to trade or transfer them from Emerald.
Yes you have to trade because you can't get all the Pokemon alone.
you can't get the black flute in leaf green but you can in Pokemon ruby, sapphire and emerald then trade it to leaf green.
Only emerald can get a johto starter however you can trade the johto shadow Pokemon from Pokemon colosseum then breed them in sapphire to get the johto starters you can also trade the johto starters directly from Pokemon xd gale of darkness.
you dont
You can only get the Johto starters by trading from Emerald or XD.
The best and easiest way to get Pokemon from Johto in Pokemon Ruby is to trade them over from other games (Gold and Silver). Pokemon from Johto can be obtained in the same generation Pokemon Emerald after the player completes the National Pokedex.
After you beat the Pokemon league in emerald you can get one of the johto starters from prof. Birch then you trade to FR or LG.
When you have completed the Hoenn Pokedex in Pokemon Emerald you can pick up one of the Johto Starter Pokemon from Professor Birch. You only get to choose one of them and to get the others you must trade with other players or copies of Emerald that picked the other starters.
I don't think you can
Obtain 200 Pokemon in Pokemon ruby, sapphire or emerald, then go to professor birch and you get to choose one of the johto starters, then you migrate the starter you chose to Pokemon, diamond, pearl, or platinum.