So the other day I studied the twelve fundamental principles of animation, a set of techniques devised by Walt Disney in the 1930s to assist in making fluid, appealing animation. One of the traits, "Appeal", pertains to character design. As charisma is important with actors, appeal breathes life into animation.
Now, the latest generation of "My Little Pony" seems to have taken the appeal to its target audience, prepubescent girls, and broadened it. In previous generations, the character appeal has been meant to target one audience.
I somehow ended up with some Generation III merchandise, and while is has many elements of the Generation IV artwork and character design, I clearly can tell I was not the intended recipient of its "appeal". Heart-shaped highlights, strongly vivid colors, and strong bright colors, along with typical American animatics and such applied.
Generation IV artwork, on the other hand, takes stylistic traits from 1990s videogames such as Animal Crossing, "moé" anime traits (while the eyes are large, they do resemble those of say...Elicia Hughes from Fullmetal Alchemist, intended to be one of those "KAWAIIDESU!!!111" kind of characters), and of course by lowering the bright polychromatics a bit, as was done with Foster's Home for Imaginary Friends. (Lauren Faust, creator of MLP:FiM, also worked as a storyboard / conceptual artist for the aforementioned series).
At the same time, the characters / scenery / imagery still maintained its solid drawing style, implying a sense of dimension. Subtle details, such as secondary action and overlapping action, abound in the animation, indicating a sense of physics not obtained with much modern animation.
All in all, character appeal, physics, and an attention to detail make it one of the most widely-appealed MLP series-es of all time.
After watching "Hearth's Warming Eve" (S2E11) I noticed that the rail line featured has a curious track arrangement resembling that of the Canadian Pacific near Yoho, British Columbia - a spiral tunnel. 
