Ling Bouvier is the child that is adopted from China by Selma Bouvier after discovering that she was no longer fertile. She won Ling after posing as Homer Simpson's wife in order to fool the Chinese authorities into thinking that Ling would be sent into a family, and not to a single mother.
She has only appeared in two episodes, first in her adoption episode. Second (briefly), in Kiss Kiss, Bang Bangalore when the twins open the door to discover MacGyver (Richard Dean Anderson) missing. (Selma was holding Ling during the scene.)