only in WI-FI events
The only way to get a Regigigas in Soul Silver is to trade it from a previous game.
Either use your masterball or put it to sleep right away without weakening it and keep throwing ultraballs.
the way to cianwood
Explore!
The only way to get Hitmontop is to evolve Tyrogue.
There is no possible way without hacking or cheating. I heard they are bringing Mew back in Pokemon Heart Gold and Soul Silver.
Currently there is no way to get a Mew in the English version of Soul Silver without using an action replay code. A Japanese event took place to get a Mew in November, so it is possible an English event will take place to find a Mew.
You can't You have to play My Pokemon Ranch on Wii and fill certain conditions. After someone will give you Mew. That is the only way of catching it. But, you can catch a Mew two but you need to beat Jhoto region and Elite Four then go to Kanto and its there in Cerulean Cave.( You need to do some stuff first.) forgot what it was SORRY
Mew Three does not exist.
you get a master ball and catch it that way
the only way to catch mew is to defeat the elite four
The only way you can do that is with the action replay code at pokeball.tk