Jethro is a short and slender caveman with fair skin, tan stubbles and a large nose, plus he carries a corn cob pipe in his mouth.
In the episode of the fourth season, "The Bedrock Hillbillies", he has a brown beard and black eyebrows, and also wears a yellow and black-striped loin cloth and a black cowboy hat.
Later in the episode of the fifth season, "The Hatrocks and the Gruesomes", he has a taupe-gray beard and eyebrows, and he also wears a brown and black-striped loin cloth with the same black cowboy hat.
- The Flintstones
- In the episode, "The Bedrock Hillbillies", he was first named as Clem Hatrock.