Ness is a young child from the country of Eagleland, and the main protagonist of the second title in the Mother series - and the only one released outside of Japan - Earthbound. Ness lives in the town of Onett beside his friend, and later rival, Porky Minch.
In Jake's Super Smash Bros., Ness is one of the forty characters capable of spawning from the Assist Trophy item. After spawning on the stage, Ness utilizes his signature PSI attack, PSI Rockin, to attack opponents. In Earthbound, PSI Rockin can deal from 40-960 damage depending on its type. In Super Smash Bros., Ness rains three straight lasers from one of the four corners of the screen across to its opposite vertex.
Don't underestimate Ness just by his looks; he's capable of using very powerful 'PSI' attacks. He stumbles upon a meteor atop a hill, and is sent on a journey to stop an alien invasion.... or something.