The episode title is a reference to the Alice Walker novel The Color Purple.
The episode makes reference to movie National Treasure: The Book of Secrets when Lisa tells about Eliza Simpson and Milhouse shows another diary. And another one is that in both movies Abraham Lincoln does something important in the past (in the episode helps them to Canada and in movie gets assassinated).
When Ralph Wiggum steps up to the stage, he then tells a spoof about 2 shows: "The King had dreams! Dreams where Elmo and Toy Story had a party!"
After showing the stop while your ahead quilting thing, they mention a famous scene from the original 1974 movie Carrie (1974), they mention when she was being crowned prom, she was splattered with pig's blood and got angry. Plus since she has supernatural powers, she gets angry and scares everyone away.
Mr. Burns outfit and mannerisms are reminiscent of Colonel Sanders.
As Eliza falls in front of the hay after she was scared by an owl, she drops her lantern. But in the next shot, she's holding it.
There is an anachronism in this episode. In one scene, there is a flashback from the diary of Eliza Simpson, which shows a scene taking place in 1860, at a party in Kentucky where the music playing is Blue Danube waltz. However, the Blue Danube was composed in Vienna, 1866.
The Canadian flag that appears in the episode is not the official flag of Canada until 1965.
Why would Lisa just focus on the Simpsons' side (her dad's side) of the family? What about her mom's side (the Bouviers) or Grampa's side of the family before they took on the last name Simpson? Or Herb Powell's side of the family (which included that carny woman that had sex with Abe for money)? Or Abbie's?
Before Abe told the story of Eliza, he was talking about D-Day.
Although this episode heavily contradicts the established family tree in The Simpsons Uncensored Family Album, Hugo Simpson I, Woody Sheeden, Remus Krupp and Mort Krupp, relatives who before were only ever seen in the book, made their first ever episode appearance in the photos Lisa found when she was searching for information on noble Simpson relatives. It seems that either this family tree was only partially retconned, or that Abe was lying about Virgil and he is not a direct descendant of Mabel and Hiram, who are related via a different branch in the family tree than that of Garwood and Clowta.