The Keeper is simply a realistic bald eagle head protruding illogically from the ground. The Keeper has a yellow beak, a white mane, and a brown neck.
The Keeper's stomach is an obvious play on surrealistic dimensions, as it is illogical for him to have a stomach. Inside leads to several other implausibly placed rooms, the first of which is a mirrored room and another room containing Giant Patrick.
The first room in The Keeper's stomach is a room with a chair and two mirrors on either side. Squidward's reflections teased him by putting their clarinets in their mouths and screeching.
The next area is a giant clarinet that Squidward chases SpongeBob across. It also acts as a cannon.
It blows them to a room with a SpongeBob-themed pinball game, and Squidward was the prize. Giant Patrick resides here. This room also has a vacuum, called "The Pressure," which blows Squidward and SpongeBob into outer space and ultimately, the front of the locker.
Squidward accidentally encounters this bird while chasing SpongeBob in Clarinetland, who had recently stolen his clarinet. The bird, upon seeing Squidward, questions Squidward, who in response says that he is looking for his stolen clarinet. The bird scoffs at Squidward's plight, and tells him that "A clarinet cannot be owned." Squidward proceeds to be rude to him and he squeezes Squidward with his tongue saying he must learn respect. After Squidward promises he's learned respect, The Keeper doesn't believe him. He then proceeds to eat Squidward. The Keeper protects the Horned Forest from clarinet owners trying to take them back. Upon meeting an unwanted guest the Keeper introduces himself and asks them to state there business. He is easily provoked and will squeeze anybody with his tongue who disrespects him. There is almost nothing known about his backstory.
The character's voice sounds similar to The Kurgan, the main antagonist of the film Highlander. Ironically, Clancy Brown portrayed The Kurgan also.
People first thought the character was voiced by James Earl Jones. In fact, it's claimed in on the site behind the voice actors, but it claims it was Clancy Brown in the original credits.