- Development Gag: One of Pinkie Pie's entries in the journal of friendship is about her efforts to create and popularize a new holiday, "Lollygabbing Day". This is based on an actual episode pitch by Amy Keating Rogers that didn't make the cut.
- I Knew It!: A good portion of the fandom postulated that Commander Hurricane was in fact the only male among Equestria's founders.
- Jossed: Conversely, this book also invalidates some of the fandom's previous assumptions about Equestrian history and the two sisters.
- There were other alicorns who raised Celestia and Luna before they were Offered the Crown of Equestria.
- Celestia and Luna did not become princesses after overthrowing Discord — instead, they reigned before Discord took over and had to retake the kingdom from him. This forces us to conclude that Discord's reign of chaos must have been relatively short, at least compared to how long the Sisters have been ruling.
- "Hearth's Warming Eve" said that Equestria was founded "long before the peaceful rule of Celestia". One would assume that "long" in this context would mean at least one generation before, but in The Journal of the Two Sisters, all six founders of Equestria are still alive when they offer the crown to the alicorn sisters. On the other hand, that line could be interpreted as long before Celestia ruled alone, after taking care of the decidedly non-peaceful threats of Discord, Sombra, and Nightmare Moon.
- Luna's nickname for Celestia is "Celie", not "Tia". The spelling is also unusual, since most fans who proposed similar nicknames for Celestia have spelled it "Celly".
- Word of Dante: According to Amy Keating Rogers, it was previously discussed that Celestia and Luna were alicorns by birthright, unlike Twilight and Cadance who ascended from another pony race. This helped dispel many fans' worries over the birth of Flurry Heart, the first alicorn born in Equestria's history. However, after Shadow Play invoked Canon Discontinuity via different origin for the Tree of Harmony, it's unclear whether this aspect is still true.
Trivia / The Journal of the Two Sisters