Which of the following is not a Flintstones character?

Lord Rockingham IX is not a Flintstones character because he is a British musician and composer, known for leading the house band for the TV show "Oh Boy!". The Flinstones, on the other hand, is an American animated sitcom that aired from the 1960s to the 1970s, featuring characters like Fred Flintstone, Wilma Flintstone, Barney Rubble, and Betty Rubble. Therefore, Lord Rockingham IX is not part of the Flintstones universe.