These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
YMMV: My Little Pony: Friendship Is Magic S3 E5 "Magic Duel"
The redeemed and nice Trixie will surely become more prominent than she already is now that it has become canon.
Wait. You mean there's an Amplifier Artifact that can make a relative weakling like Trixie so powerful she outstrips the pre-ascension Twilight, but slowly corrupts the user to evil? Where did it come from, how was it made, how did Trixie find out about it? And it's now sitting in Zecora's hut where potentially anypony could find it or one of the cast could retrieve it and use it in a dire situation? The Alicorn Amulet is a tanker truck of fanfic fuel all by itself.
The existence of an age modification spell lends itself to so many stories, even if only ponies like Celestia are powerful enough to use them.
While there's no confirmed Rule 63 spell, the possibility one might exist is prime for fanfic (not that there aren't already numerous Rule 63 works out there).
Foe Yay: Not that fans didn't have a reason to ship Twilight with Trixie, but now the shippers have some genuine shipping fuel. "I can't stop thinking about Trixie!"
Genius Bonus: Another episode, another reference to Hermeticism. Twilight's pose at the end, with the infinity symbol overhead, resembles the Magician tarot card sometimes associated with Hermes Trismegistus. The "light within" from the Crystal Empire, known most commonly as "the Absolute" or "the Monad", is also called "the Infinite" in some traditions. Guess what happens when Twilight summons the infinity symbol? She has pure white light bursting from hernote in the deceptively edited preview. What do the myths state about Hermes Trismegistus? He leads things (especially the Fool) out of the darkness and into the light.
"I heard she told a few ponies she was going to remake Ponyville!"
On a Cross and Arrow was a fanfic about the mane six meeting their colt counterparts. In the episode Magic Duel, one of the "magic tricks" that Twilight does is turn Applejack into a stallion. It was really just Big Macintosh painted in Applejack's colours, which is what that story's version of male Applejack looked like (while the other five had regular stallion proportions).
Shortly before season 3 started, there was this fancomic where Twilight pulls off the exact same age changing trick.
Lauren Faust had intended for Zecora to be Twilight's mentor in Ponyville. Guess what happens in this episode?
Previews for the season stated, "One unicorn will learn her destiny!" over a clip from this episode, which has Twilight walking on water....
Fluttershy's blind bag toy was a Palette Swap version of Rainbow Dash. In this episode, she dressed up as Rainbow Dash.
Take That, Scrappy!: Snips and Snails get their just desserts when they are abused by Trixie, whose cart they ended up wrecking through their own stupidity in her first appearance.
The Woobie: On the other hand, if you realize that Snips and Snails were Trixie's strongest supporters and admirers in "Boast Busters", it's a little sad to see them being cruelly tormented by their former idol purely For the Evulz.
Bow before the Great and Powerful mane article HERE