Nintendo didn't seem to keen on releasing Mother 3 for the Gameboy Advance outside of Japans, so a group of fans banded together and took localisation duties into their own hands. Nearly two years after the project first started, the Mother 3 fan translation website has launched version 1.0 of their labour of love. Now mind you that actually utilizing the translation requires the use of a ROM, which in turn requires the use of an emulator, which pretty much equals being shady. Pay special attention to the first step listed in the instructions on the web site.
Import a copy of the game, if you can find one. It's not cool to brazenly pirate stuff! Itoi, Nintendo, HAL, and Brownie Brown worked hard on this game. Can't find a copy? Consider buying some official merch (below).
Ignore the can't find a copy bit. Buying official merchandise in no way excuses pirating a copy of the game. Honestly I was hesitant to even mention the project due to such concerns, but now an entire page of my email client is filled with Mother 3 subject lines, so there you go.
The Mother 3 Fan Translation [Official Site - Thanks Everyone]