Some stuff I don't think has been brought up yet, or maybe I just missed it...
Our brief glimpse at Yakyakistan.

Actually, the second time through, I noticed that they specifically mention at the beginning that this place is so far north that no pony has ever been there. It's kind of funny that, for all the stereotypical Russian-ish, barbarian-ish, Viking-ish personality they gave the yaks, they seem to live in this mysterious Shangri-La. And sure enough, even Pinkie is denied entrance at the very last moment.
Pinkie still gets Looney Tunes gags, like her periscope hair:

Rarity never gives up on trying to fix that vase.

A very Mad Men train ride. And a bum.


I's had all's I can stand, and I cans'k take no more!

The animators showing off a bit.

It's that spiky-haired pony again!

We've been over the Beatles' cutie marks, a peace sign, a yellow submarine...

...but what's this?

Relevant to the recent helmet safey discussion:

(Also, Berry Punch spends a lot of this episode drinking from those pools. I guess she's just really thirsty!)

Fancy store signs

I love how Twilight gets progressively more excited at her profile.

...dancing...

That's right!

But she's afraid of quesadillas.

Headless Horse wrote:The Crystal Empire is apparently a combination of Narnia and Gondor, judging by the boundary marked by a lantern and a stairway up a cliff.

