Princess Twilight states that she has enough material to give Starlight three years of friendship lessons. Twilight had three years, or seasons, of friendship lessons before she became Princess.
Rarity didn't utter single word in this episode, ergo making it the only season premiere in which one of the main characters doesn't have a single line of dialogue. It's also the only Season 7 episode where Rarity appears but doesn't speak.
This is the only season premiere that's not a two-parter.
This is the second season premiere where Twilight does not fly after part 1 of "The Crystalling".
There are two possible theories as to why Rarity has no lines in this episode. One theory is that her voice actress, Tabitha St. Germain was presumably unavailable. Another is that she sat out of the season premiere altogether after objecting over it not being a two-parter.