- Awesome Music: The soundtrack being by Yuki Kajiura, pretty much all of it qualifies, but special mention must go to the OP, "The Other Side of the Wall".
- Base-Breaking Character: Beatrice. You either love her for being the team's moral compass, having a useful ability for espionage and being the closest thing the main cast has to a normal person or hate her for not being as badass as the other girls.
- Ear Worm: The opening song "The Other Side of the Wall", big time.
- Fanfic Fuel: There are only 12 episodes, but the case numbers go up to 24. What happened in the cases that were not shown?
- Les Yay:
- The end of Episode Two reveals that Ange and Charlotte knew each other. Ange purposely sabotaged the mission to assassinate Charlotte, so she could simultaneously save Charlotte's life and make her an 'ally' to the people she works for at the same time. She put a great deal of planning and took a number of risks that would have put her life in danger for the sake of Charlotte.
- The dialogue between Ange and Charlotte at the start of episode 3 is... suspicious, to say the least. "Let's run away together". "There is a white house waiting for us in Casablanca". And worst of all, "With the Wall gone, we can be together and it won't matter who knows it".
- By episode Six it's getting hard to believe that the writers aren't doing this intentionally.Princess: ''I want to stop having to hide our relationship, Charlotte."
- Episode Eight goes into their origin story showcasing how they became good friends quickly and why they are so devoted to each other.
- Episode Eleven has Ange state in her internal monologue that despite losing everything, she kept fighting and wanting to meet the Princess again is what helped keep her fighting.
- In Episode twelve the Princess leaves Ange a message which starts with "My turtle dove". In case you don't know, turtle doves are a symbol of devoted love (romantic, usually).
- One of the last shots of the first season is Ange and Charlotte holding hands as they relax on the beach. Earlier that episode, there's a long, emotional scene of Ange Bridal Carrying Charlotte, ending with the latter saying she will "break the wall around [Ange's] heart."
- Ange's Image Song is "Take Me Up Higher" and Charlotte's is "Into The Sky." The other characters' image songs have no obvious connections.
- Beatrice loves Charlotte too. She screams it aloud while falling through the sky at the end of episode 3.
- Eleanor/Prefect's attitude towards Dorothy (admiring her greatly for years after leaving Spy School, looking back on their Christmas carnival together very fondly) has significant Les Yay undertones.
- Quite a few fans think Dorothy and Beatrice have some Les Yay going on between them. Certainly there is solid chemistry between the pair, especially in episodes 6 and 10.
- Turns out the OST version of "Moonlight Melody" is a duet sung by Dorothy and Beatrice, making the potential romantic undertones of the song much more prominent.
- Moe: all the main characters are drawn in a moe style, but Beatrice really embraces the aesthetic.
- Narm: The almost excessive amount of amoral, almost cartoonishly evil abusive dads.
- Nightmare Fuel: Ange paints a rather chilling image of Charlotte's situation in Episode 8. As someone who is trapped in the role of her friend's identity, her only option is to play the part to perfection. Having taken the Princess's place, she would be executed if anyone ever found out.
- Rescued from the Scrappy Heap: Thanks to Character Development in the later episodes, many fans' opinions of Beatrice have softened to the point where some even consider her their new favorite character.
- Spiritual Successor: When people found out about the spy elements, many comparisons to Production I.G's adaptation of Joker Game surfaced. Some people went as far to say that the series served as Joker Game's cute girl-themed Distaff Counterpart. The ahow itself may have a Spiritual Successor of its own in Release the Spyce.
- Tainted by the Preview: From early promotional material, Princess Principal looked like a "cute girls doing cute things" Slice of Life show that just happens to be set in steampunk Victorian London. It's an original anime with a misleading title, so there wasn't much to counter that assumption. Nobody could have expected the show getting into serious, hardcore spy intrigue in just the first episode. Many people wrote the show off as a waste of time without ever learning what it was really like.
- And then there are those who only saw the title, assumed it was some kind of high school romantic comedy, and dismissed it instantly without ever seeing so much as a single image.
- The Woobie: Poor Beatrice. Her Mad Scientist father experimented on her, forcibly replacing her larynx with a mechanical implant; her peers ostracized and mocked her for being a "machine girl"; and to top it all off, the one girl who accepted and loved her drags her into the world of espionage in a bid to usurp the throne.
YMMV / Princess Principal