Creation
Kenny Cavanaugh was created for the Smallville comic book series. He was never seen or even mentioned in the tv series or the Season 11 comic books.
Story
Back in 1989 a young boy named Kenny is hunting in the woods with his father. After they split up to finde a deer, Kenny witnessed his fathers death – he was crushed by a meteor.
Many years later, Kenny became a metahuman with the powers of invisibility and lived his life in the woods. There he attacked Jonathan Kent and took him in his cave. After Jonathan woke up, Kenny asks him if he’s his new dad. Jonathan figures out who Kenny is, and what happend all those years ago. It was Superman who freed Jonathan from Kenny.
Later, Kenny was arrested by the police and transfered to an asylum by orders of Lex Luthor. What happend to him there is unknown.