Well there's no way this is true since Kirby's appearance was decided during Dream Land's development. It's not like they put him in some game prior to that with the intent to make him his own character later, he literally didn't have a design at first.
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The Temple of Kraden, a forum for fans of Golden Sun:
http://z9.invisionfree.com/The_Temple_of_Kraden/index.php?act=site