KG's protruding jaw actually has quite a story around it. When KG was a baby, his mother dipped him into the river Styx (the river that produced such hits as "Come Sail Away" and "Mr Roboto"), holding him initially by only his fully grown chin beard.
While the rest of him was immersed*, his chin was left exposed, and thus allowed to grow naturally, a slave to his own flawed genetics. The chin grew large as was the habit in his family, and thus next to the rest of his perfectly sculpted body grew in proportion to his large frame, his chin became freakishly large.
This is the reason why during times of passion his comments are always profanity laced. His chin screams out in protest of its imperfection.
*And his knees. She dipped his whole body except for his chin and his knees. Not the best thought out dipping of the river Styx.