In The Simpsons's episode "The Great Louse Detective" several attempts are made on Homer's life and The Simpson family has to figure-out why. When it's reveled that it's their mechanic, his name and reason are both reveled. As it turns-out his name is Frank Grimes Junior and he's the son of Frank Grimes (Homer's deceased enemy). Jr. wanted revenge on Homer for being the reason and the cause of his dad's death. Jr. was an illegitimate child, who's father tended to really like hookers.