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 S1 E6: "Boast Busters"
Accidental Aesop: Though the official moral is that it isn't arrogant to use your talent when you need to, another lesson might be "those who boast will eventually be called on it".
This has been eased a bit by her later appearances. In "Magic Duel" she's far worse, but was under a spell at the time and shows actual humbleness once she's freed of it. And in the comics she's done a full Heel-Face Turn.
Designated Hero: Applejack, Rainbow Dash, and Rarity have been seen as this by many people who dislike this episode. And the fact the three were showing off in front of Trixie and the crowd makes them look petty and hypocritical.
Also, astronomy buffs might notice that the Ursa has a certain constellation on its flank...
Also, the Ursa Minor has a long tail, just like in the myth of the constellation.
It also takes a rudimentary knowledge of Latin to know that 'ursa' means 'bear,' and that Ursa Major and Ursa Minor are the official names of the 'Big Dipper' and 'Little Dipper,' respectively.
This could also be seen as Foreshadowing for the reveal at the end...
Hilarious in Hindsight: In this episode, Twilight's genuine magic beats out Trixie's parlor tricks. Two seasons later, Twilight's parlor tricks beat out Trixie's genuine magic. She just cannot catch a break.
Rarity's disgust at having green hair. When Season 4 introduces the "friendship rainbow" which incorporates the colors of the Mane 6's coats, Rarity's white occupies the middle position in the spectrum where green would normally go.
Love It or Hate It: This episode is one of the most popular and well-known episode of the show, despite also being of the most hated on the show.
Trixie In A Leather Saddle: Trixie is probably the biggest Draco in Ponyfandom, easily edging out Gilda and Discord. Probably attributable to the fact that unlike Gilda, she didn't do anything morally wrong (outside of being an arrogant jerk), she's more adorable physically, and for what she did compared to what others have done, gets the harshest karmic retribution.
The Scrappy: Trixie, Snips and Snails, and/or the mane six depending on who you ask.
The Woobie: Twilight Sparkle thought her friends would hate her after showing her magic since Trixie's magic show.
Jerkass Woobie: However while Trixie herself was showing off, she suffered a slight guilt and admitted to lying just to make herself look better. In Season 3, where she returns in "Magic Duel", we find out that she did have it rough after the events of this episode.