The Grumpers are a race of short cavemen, enemies of Popeye. They first opposed him in the Thimble Theatre storyline "The Grumper Invasion" (1966), and became recurring adversaries when they reappeared in "The Return of the Grumpers" (1975), planning to attack the sailor again.
Millions of years ago, when cavemen left their caves, some of them decided to live underground. Only the short ones are able to live there, but even those keep hitting their heads on the roofs of the tunnels, which generates permanent headaches. The Grumpers hate our world of roads and sidewalks, as they hit their heads on the cement and are unable to rob us. They especially hate Popeye, for his "spinach-eating fist" which delivers even more headaches. For all the above reasons, they have become rude, horrible and crooked. In their return appearance, they go so far as beating up Swee'Pea with their clubs and demanding a ransom of a billion potatoes and a box of mint drops.