Let’s start with Carlo's name. Karl Marx was a political philosopher in the 1800’s who started Marxism. To make a very long story short, he said that capitalism would be overthrown by socialism, which, if placed in a 375-degree oven for two hours, would end up as communism. That’s the skinny. So Carlo may reflect some of these socialist tendencies, or at least the anti-capitalist ones. Then there’s also Groucho Marx, a comedian in Kerouac’s time period. So that’s it: Carlo is an anti-capitalist comedian who may or may not want to sleep with Dean.
Carlo is based on Allen Ginsberg, a friend of Kerouac who was openly gay. Carlo isn’t quite so open, but there are some hints that he may be interested in Dean. We always see them on the bed together, and at one point Carlo tries to get under the covers with Dean and Marylou. Dean does not return these potential advances in any way.
Carlo and Dean together define what Sal calls "a new Beat Generation" of "sordid hipsters." There’s nothing light and Care Bear-y about Carlo. His poetry is dark, he’s always in the doldrums – "sordid" certainly seems the proper word. He’s also the voice of reason or, as Sal says, "The Voice of Rock," asking for explanations and reasons behind Dean and Co.’s crazy actions. They, of course, are unable to provide such reasons, and Carlo ends up on the fringe of the story.