Grandpa Abe Simpson mentions Julius and Ethel Rosenberg. Ethel Rosenberg & Julius Rosenberg were executed in 1953 after being convicted of conspiracy to commit espionage, for passing secret information about the US atomic bomb to the Soviet Union.
Footnote in Mabel Simpson's cookbook: "After the patrollers left, the circus clown made the following comment, which suggests an unusual aptitude for predicting twenty-first century currency values: 'Why do I always ask for a nickel? That's like twenty bucks in 2010 money.' It may have been intended as humorous, although my daughter didn't mention anyone laughing. This clown seemed to say many things that were humorous to him, but not to those around him, nor to me. But since my daughter repeated them all, I thought I would record them here. Enjoy them, people of the future!"
Grandpa Simpson's great-grandfather was half black, making him 1/16 black, so Homer is 1/32 and Bart, Lisa, & Maggie are 1/64.
As a joke, the "Krusty" Klown in 1860 says "Why do I always ask for a nickel? That's like $20 in 2010 money!" In actuality, an 1860 nickel would only be worth about 90 cents in 2010.
The title is a reference to the color of the Simpson family's skin.