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 S2 E20 "It's About Time"
The "Star Swirl the Bearded Wing?" A maximum security wing of the Canterlot archives where powerful and dangerous spells are kept and Pinkie was let in?
Just the fact that time travel via magic is possible. Okay, okay, Twilight blew her one chance with that specific spell, but Future!Twilight suggested there were more time-related spells in that wing. Maybe it only works once per point in the past.
A town built on (er, near) the gates of Hell, populated with a number of spunky young Badass girls and their friends, drawing from a variety of physical and magical powers to keep creatures from said gate in check? And characters named Spike and Angel?
On a much smaller scale, Twilight's really cool birthday present. She wanted information on the cause of a future disaster. Pinkie tells her about a future birthday present instead. Wouldn't it be very Pinkie-like if she were more on target than anyone realized?
Another non-Ponyville town, LasPegasus, is confirmed, and implied by Rainbow Dash's figure of speech to be on an opposite coast from Fillydelphia.
Twilight's outfit, as well as the ones Pinkie and Spike wear, and that's all we're going to say about it.
Harsher in Hindsight: The episode, and its moral, take on a whole new meaning after the Season 4 finale. Twilight freaks out about a possible disaster in the future, and learns not to worry about the future. Turns out that a real disaster has been brewing ever since this episode. And it's probably for the best that Twilight doesn't worry about it until it's time...
They Wasted a Perfectly Good Character: Many fans were expecting Doctor Whooves to do something special in this episode, even if it was just a Funny Background Event. He shows up, but only to act as a normal background pony. He could be maintaining his cover (How funny would it have been to give him shifty, nervous eyes during the scene in question?) but in all likelihood the studio probably thought they reached their Doctor Whooves nod quota for the season and don't want to over do it.
Well, we do get the irony of the guy who looks like The Doctor as one of the ponies laughing at Twilight claiming to been visited by a time traveler.