Pokemon is made by Gamefreak, buddy.
And I'm not sure what boss you're making a reference to.
I'm sorry, you're right, its the Maker of Earthbound that did pokemon, but he mainly works with HAL, I guess you can see the assumption now...
the boss is Giygas!
in Mother 1, He's pretty much Mewtwo, hell, Mewtwo was Designed off of Giygas
In Earthbound (mother 2) He's the Creepiest boss ever!
Here's a wiki page on him!
http://earthbound.wikia.com/wiki/Giygas