Douglas Klump is part of the team commonly known as Fat Man and Little Boy. Klump is Little Boy.
He and his partner are a pair of low rent do anything hoods that are most often used to dispose of the bodies of other peoples kills. A job that they seem to be totally incompetent at doing and as shown in the Sin City Yarn titles Fat Man and Little Boy being "Roundedly disciplined" for not completing the job as instructed.
Both mean also have as Hartigan put it "Delusions of Eloquence" as they use pseudo-poetic words as part of their normal means of daily conversation in a poor attempt to seem cultured, refined and educated.
They make several appearances in different Yarns such as Fat Man and Little Boy, A Dame to Kill For and That Yellow Bastard.
Rick Gomez portrayed Klump in the 2005 movie adaptation.