- Accidental Aesop: Given a lot of people were frustrated at Pinkie Pie for asking too much of Twilight to keep a secret she shouldn't have in "Green Isn't your Color", this could be seen as a personal one for Pinkie Pie: some things are easier said than done.
- Alternate Character Interpretation: The various scavenger hunt clues relate to places and ponies Pinkie met earlier, all of which had some rather convenient dialogue about foals and royalty. Since Mayor Mare at least knew about the news, it's possible that they were all in on the secret from the start; if Shining Armor and Cadance sent advance notice to the Cakes, it's entirely possible they did so with the others, too.
- Additionally, some people have theorized that Twilight may have actually figured it out very quickly and was just trolling Pinkie to get back at her for when she had to go through this.
- Epileptic Tree: The moment the synopsis was released, the fandom went into a flurry trying to guess at what the secret was. Many fans correctly thought Cadance is pregnant—a rumored plotline that had already been flying around since after A Canterlot Wedding and hinted at by the mid-Season 5 poster put out by Hasbro.
- Fanfic Fuel: TWILIGHT GETS A DOLL! SHINING ARMOR GETS A DOLL!! POSSIBLY EVERYONE IN THE FAMILY GETS A DOLL!!!
- Also Smartypants x Brutus Force.
- The adventures of Smash Fortune scream for expansion.
- Genius Bonus: Shining Armor's doll is named Brutus, after the ancient Roman political family. Shining Armor himself is both an aristocrat and wore a quasi-Roman military uniform during his time in the royal guard.
- Harsher in Hindsight: As the years pass by and a new season is introduced, the episode has become something of a metaphor for the series in real-life: Pinkie symbolizes the person who's responsible for the release of some episodes ahead of their intended airdate and ends up ruining the surprise for everyone else. Whether it was either by accident or on purpose, with or without good intentions, it doesn't change the fact that it's distasteful and simply not in their right to do so.
- Case in Point: Someone illegally leaking some episodes for Season 8 in December 2017 when Season 8 is officially scheduled to start in 2018.
- Cranked Up to Eleven with the last half of Season 9, in which a broadcaster in the Netherlands released every episode of the final half of the season in one day. They pulled it after the fact, but still.
- Heartwarming Moments: Twilight's reaction to the news that Shining and Cadance are having a baby is definitely this.Twilight: Oh, I love you guys! And I can't wait to meet your little foal!
Shining Armor: Neither can we.
- Hilarious in Hindsight:
- Suspiciously Similar Song: The polka music that plays when Pinkie Pie is making her cupcake deliveries sounds awfully similar to the Clarinet Polka.
- Tough Act to Follow: It was a tall order for this episode to try and top the last episode, due to that one being a massive Wham Episode. Unlike "Lost Mark", this episode is more standard Slice of Life and Cringe Comedy, even if it does change the status quo by announcing Shining Armor and Cadance are having a baby. Whether that makes "Pinkie Pie Knows" better or worse is left to the individual viewer.
- The Un-Twist: Given some hints on the Season 5 poster and the plot about Pinkie keeping a secret about Cadence and Shining Armor, many thought that the couple having a foal was too obvious a direction and expected the secret would ultimately turn out to be something else in the end. Turns out the two now being expectant parents is exactly what happens. Possibly for the best, no attempt to hide this is made in the actual episode, which directly gives it away before the opening credits.
YMMV / My Little Pony: Friendship Is Magic S5 E20 "The One Where Pinkie Pie Knows"