Symbolism, Imagery, Allegory
First things first: what the heck is a Sambo doll? In a word: racism. This little puppet is racism encapsulated. It's a caricature of a black man drawn along the crude and evil lines of mid-century bigotry:
Shake him, shake him, you cannot break him For he's Sambo, the dancing, Sambo, the prancing, Sambo, the entrancing, Sambo Boogie Woogie paper doll. And all for twenty-five cents, the quarter part of a dollar… Ladies and gentlemen, he'll bring you joy, step up and meet him, Sambo the – (20.71-5)
When the narrator further examines the paper doll that Clifton was selling, he realizes that Clifton controlled the doll with a thin black string that was invisible to the audience. Clifton puppeteers the flimsy black doll in much the same way that the Brotherhood manipulated both Clifton and the narrator, or the way the narrator has been manipulated his entire life, or the way black people have been manipulated for white people's entertainment (think of the battle royal, for example).