Every Simpsons fan knows of Ralph Wiggum, the special needs kid who is the son of the local police chief. Ralph is the character who interrupts the show with dialogue that is unintentionally funny. His teacher, Ms Hoover does not quite know what to do with him, the other kids in his class stay clear of him, and the rest of us get a good giggle from some of Ralph's classic lines, i.e. My cat's breath smells like cat food.
Ralph debuted in the fourth season of the show, as a lonely kid in Lisa's class. She sent him a Valentine, because she felt sorry for him, Ralph took it the wrong way and developed a crush on her, leaving Lisa embarrassed and then angry, eventually breaking Ralph's heart. Later, Ralph wins the respect of Lisa and her classmates by proving himself to be a reasonably talented actor. In this episode, Ralph is perfectly intelligent, despite being socially awkward. In later episodes, the character developed into a kid who was dim, but eternally optimistic. And that optimism is the reason that we all love him.