Emoji Emoticons Enabled for All by frostyplace App!
The inimitable iJustine has tastily blog snacked about an App Store goodie named frostyplace (iTunes / $0.99), a Japanese RSS reader that by-the-way works around the iPhone's limitation of only allowing Emoji (the massive emoticon collection used in Japan that adds to smiley face things like panda bear, train station, and mountain) on it's official Japanese carrier.
Basically, you download and install the app, use it to browse some Japanese RSS feeds (i had to do it for a couple minutes, exiting and re-doing it 3 times), and then the Emoji option will miraculously appear in your settings and you're golden.
Check out her site for the details and instructions, but I tried it and it worked for me. Let us know how you do!