Yeah, Earthbound's a great game and everything. Really. But, wouldn't it be awesome to be able to play the game with one hand, leaving the other free to do... other stuff?
Turns out that you totally can do that.
Just use the control pad to move (duh). You can then use the L button to check/talk to/generally interact with everything in the world. Then you can use Select to bring up your status screen,
then hit L to bring up the rest of your menus. From there you can use the control pad for navigation, L for 'confirm' and Select for 'cancel'.
Now, I'll admit that this can get a little tedious when you have to do stuff like inventory management, but it's totally possible to play this game with your left hand while your right hand is otherwise occupied (*snicker*).