Sluggo is Nancy's best friend in the Nancy comic strip. Their relationship appears to be platonic. Little is know about Sluggo's family, but they are poor, because they are unable to keep the plaster patched, a chunk of the bathtub is broken off, and Sluggo has to watch ballgames through a knothole in the fence. Sluggo looks like a tough guy, but he is never seen to be mean.

Sluggo is the arch nemesis of Mr. Bill, along with Mr. Hands. They're largely responsible for all the pain and suffering that Mr. Bill lives each and every day of his life.