That being said, I'm still not sure why it has gathered quite the following it has. I mean it is surprisingly good for what it is, but 29 pages of pony pictures and 4chan going insane for a while. Seems a bit much.
The full range of expressiveness of the characters makes it uniquely suited to pictures and gifs. I mean, The Powerpuff Girls is entertaining to watch, but there's no angle in posting them -- they just have a series of stock expressions.
Who needs 13,000 pictures of that?
Also, the fact that My Little Pony gets the ignorant to troll themselves is great.
Because the series has a history it allows those who think like conservatards to make their classic mistake: they build their opinions on assumption -- in this case the assumption that the show is the same as the 80's cartoon -- and they then hold that their opinion is necessarily right even though there's no logical necessity that a reboot has to be anything like its predecessors. Those on the "in", as they actually have knowledge, get to watch those idiots' opinion run smack into a reality that shows an entirely different picture. So it allows them to feel the smug superiority of a superior education that an Ivy League liberal enjoys.
A show like Spongebob just doesn't have that trolling capacity. It looks like a random cartoon for babies; but that's all there is to go on and nobody's gonna stick their neck out on just that. I've never watched a single episode so I'm quite aware of what Spongebob pics look like from the outside. It just looks like a random oddity. There's no great "WTF" because you don't really know what a show like that is supposed to be.
My Little Pony, OTOH, has a hook that gets all the little fishies to jump right in the trollboat.