Some items seen in the library are Everybody Poops: The Video, Yu-Gi-Oh! Price Guides, and Itchy & Scratchy books on tape.
Henry wipes his mouth with the Magna Carta, an important document in the 1200s.
This is not the only time that Homer wipes his mouth with an important document, as he also does so with the sacred parchment at a meeting of the secret Stonecutters society in Homer the Great. In Make Room for Lisa, he licks the Eighth Amendment off the Bill of Rights.
When Henry VIII and Anne Boleyn are making love, she says "Oh, Henry!" which is a possible reference to the candy bar, Oh Henry!
Homer says to Bart in his dream to "get out of my dreams and into my wife", a reference to the song, "Get Outta My Dreams, and into My Car", which in turn was inspired by a line in the song You're Sixteen.
Homer sings a variation of "I'm Henery the Eighth, I Am".
Marge says that one of the good things about Elizabeth I's reign is the fact that it gives various British actresses a chance to play her when they reach a certain age, a reference to the frequent portrayals of Elizabeth in film and television by famous actresses such as Glenda Jackson, Helen Mirren and Judi Dench.
The music in Bart's opera is in fact Mozart's Eine Kleine Nachtmusik with lyrics referring to flatulence. "Eine Kleine Nachtmusik" isn't an opera however.
The three more talented brothers of Lisa are three members from the Jackson Five.
Salieri was a man and he was not related to Mozart at all. He also gained fame and the emperor's favor before Mozart did, and may have tried to keep Mozart from moving up — the opposite of the portrayal in the episode. Mozart's real sister was actually named Maria.
Mozart was portrayed as a child who died at about age 10 of a cold that probably became pneumonia. However in reality he died when he was 34 and of an unknown disease.
In the Sacagawea segment, the chief (Homer) says that Sacagawea's (Lisa) name meant "little know-it-all." It is said to mean "bird woman."
In the Henry VIII segment it has Jane Seymour getting executed; in reality she died in childbirth, but after she had the baby boy — Edward VI — that Henry had long sought.
It also shows Henry executing all but his first wife; in reality only the second and the fifth were executed. They were commoners Anne Boleyn and Catherine Howard.
Marge explains how eventually Elizabeth I became queen and that England's power was never greater; in fact England reached its greatest power about four centuries later as the British Empire. Also in real life this is the order after Henry — Henry, his son Edward, his cousin Jane for 9 days, his daughter Mary after Jane's execution, and Elizabeth after Mary's death.
Lewis and Clark are portrayed as being complete morons; but this is because they are being played by two simple-minded residents of Springfield.
Order of King Henry's wives in the episode — Margarine of Aragon, Anne Boleyn (beheaded for giving birth to Elizabeth I and for adultery), Jane Seymour (beheaded for her voice), Otto (beheaded for being a boy), unnamed wife (suggested Catherine Howard, beheaded for unknown reasons), old unnamed wife (beheaded as she was old and Henry didn't want to kiss her). King Henry's wives in real life — Catherine of Aragon (annulled), Anne Boleyn (beheaded for adultery and for not giving birth to any sons that survived after birth), Jane Seymour (died giving birth to Edward who died at age 15), Anne of Cleves (annulled), Catherine Howard (beheaded on grounds of adultery), Catherine of Parr (became a widow after Henry's death).
In the second segment the tribe leader said that he sold Sacagawea to Sharbinno (Milhouse). In real life Sacagawea was given to Sharbinno through a poker game and he already had another wife.
The epilogue said that Sacagawea went on to model for butter boxes. However the box their probably talking about didn't release until after Sacagawea's death.
Marge said that you could trade a Sacagawea dollar at a bank for a real dollar, However, you can sell a Sacagawea dollar for large sums of money and get rolls of them at a bank.
All of these errors can be justified as gaps in Marge's knowledge or she made parts of the story up to make them appeal to the kids.
When Salieri drinks a glass of wine after successfully ruining Mozart's symphony, she promptly falls asleep. However, before she serves Emperor Burns a glass of wine, she only pours the sleeping agent into his glass. She probably also put it in another glass by mistake.