Sambo Doll

After the Narrator returns to Harlem from downtown, he runs into Tod Clifton selling paper sambo dolls on the street. The Narrator is stricken with rage, and feels betrayed by Clifton, a once active and vocal member of the Brotherhood, now selling racist caricatures on the street. 

The Sambo dolls share a name with the titular character of Little Black Sambo, created by Helen Bannerman, although not intended by Bannerman to be racist- the crude and stereotypical illustrations of Sambo and other black characters in the original print; the name Sambo, which was used at the time as a racist epithet to depict "the lazy, grinning, docile, childlike, good-for-little servant", according to Ferris State University's Jim Crow museum; and the more explicitly racist knockoff versions distributed around the country- would end up making Little Black Sambo one of the most infamous iterations of the 'pickaninny' archetype. 

As the story takes place in the 1930s and was published in 1947, Ellison knew that his audience would be familiar with the character of Sambo, and all of the extra baggage that comes with the use of the name. Ellison uses the name Sambo to trigger an emotional response in the reader, to get them to feel the rage and disgust that the narrator felt seeing a once proud ally reduced to selling the opposite of what he was preaching a few weeks earlier. 

The dolls were described as having a kind of 'energy' when Clifton was performing with them, appearing almost alive, especially after the Narrator spits on the doll Clifton was performing with.   Once Clifton and the crowd leave however, the Narrator examines the doll, and "half expecting it to move" he instead finds it just a "still frill of paper". I think this is a way of Ellison showing just how real the effect of negative stereotypes had on the black community.

Finally, the mention of the dolls two faces, which the Narrator describes as "like a mask", calls to mind the lesson that he was told from the beginning of the book- act like a yes man, while undermining them with those yeses- "agreeing them to death and destruction".

Hotel Chthonian

In chapter 14 of Invisible Man, the narrator is introduced to the Brotherhood at a hotel called the Chthonian. According to Webster's Dictionary, Chthonian is defined as- 

"Designating, or pertaining to, gods or spirits of the underworld; esp., relating to the underworld gods of the Greeks, whose worship is widely considered as more primitive in form than that of the Olympian gods. The characteristics of chthonian worship are propitiatory and magical rites and generalized or euphemistic names of the deities, which are supposed to have been primarily ghosts."

Ellison is not an author who would just give a name to a location without it having special significance, he keeps the name of college out of the story to make it ambiguous, but made sure to name the paint factory to make that setting a metaphor for the visibility of blacks in America. 

The fact that the group is at that moment striving for anonymity (as seen when they discuss Bigger being more useful with the police not knowing his true identity), and the fact that their meeting place is so closely related to the underworld is no coincidence. The Brotherhood is attempting to form an underground organization, and by installing the Narrator and other people in the Brotherhood as representatives and leaders of their community, they are effectively establishing a world just below the visible one, much like the underworld. 

Of course, the underworld has natural negative connotations, possibly indicating that the Brotherhood may not be as virtuous as the Narrator takes them to be.