"The Hatrocks and the Gruesomes" is the nineteenth episode of the fifth season of The Flintstones. It originally aired on ABC on January 22, 1965. It features the characters of the Gruesome family, a monstrous family similar to those seen in The Addams Family and The Munsters, who were introduced in the 1964 episode "The Gruesomes"
Fred fears a visit from Jethro Hatrock, who had his family in a feud with the Flintstone family years ago, but the visit is a peaceful one, since he is on his way to the World's Fair. But Fred's generosity goes too far, and the entire Hatrock family extends their stay in the Flintstones' house, and Wilma does not like it. So, Fred enlists the help of the Gruesomes, but to no avail. But finally, Fred decides to drive them out with something that hillbillies hate the most: bug music!
- The title and the plot of the episode is a spoof of the hillbilly feud between the Martins and the McCoys in West Virginia in the late 19th century.