Earl Bighead is a very large, mean-looking, purple bulldog. He has yellow eyes, red hair and large lower teeth that protrude from his mouth and wears a spiked dog collar. He was initially homeless, and is occasionally locked up at Dr. HP Marten's Institute for Questionable Experiments, due to his viciousness. His "fairy dogmother" frees him from Dr. Marten's lab.
Earl enjoys harassing Spunky, mauling Rocko, Ed, Dan the Fly Man, and basically anything else that is alive. Bev found him digging up her flower garden. After yelling at him for the first time in his life Earl was sorry for misbehaving. As soon as they befriended each other he was adopted by Bev. Ed hates him and Earl hates Ed but is loving towards Bev as she loves him and takes care of him. Deep down Earl is lonely. All Earl really wants is a loving family and a permanent home. His vocal effects are provided by Tom Kenny. He belongs to Bev, Ed, and Rachel as of "Frog's Best Friend".
Earl has yellow eyes with black pupils, red hair and large lower teeth that protrude from his mouth and wears a spiked dog collar.
- A dog similar to him appears in a MTV bumper that Joe Murray made. In it, a cow very similar to Heffer also appears. The dog has yellow eyes and the color of fur that Earl has, and is also viscous.
- Earl can be seen as the opposite of Spunky, whereas Spunky is dimwitted, but loyal and nice to Rocko and most other people he comes across, Earl is cunning and smart, but also mean and will attack anyone aside from Bev.
- Earl is one of the many characters not to appear or be mentioned in Rocko's Modern Life: Static Cling, even though it is always unknown whether Earl is alive, deceased or incapacitated after 20 years.