[quote]What I don't really get is MLP[/quote]
MLP surprised everybody, in all fairness. They got their own fan conventions in less than a year and had a reception that even for a Lauren Faust show was pretty ridiculous. I genuinely started watching the show because Lauren Faust was advertised as the showrunner and enjoyed it well enough, but I never could have anticipated what that show became. Has several comics, several seasons, and a fan-based community that is as welcoming as it is unnerving. Grouped up with a few of the local fans at Youmacon a few years ago and they were a lovely group of awkward nerds. Perversion of fandom will happen with anything, so you need to just distance yourself from that aspect. 

[quote]You're talking breadth, I'm talking depth.[/quote]
I'm talking about [i]both.[/i]

[quote]I'm also talking about the source material. [/quote]
So am I. Everything I mentioned was official material. 

[quote]You could write your own novel using those characters[/quote]
I'm not talking about fanfiction.

[quote] That material in this case would be, like, the video games and saturday morning cartoon.[/quote]
It would also include two comic book franchises, several novellas, and several cartoons (not just one).

[quote]"how come all these fandoms latch on to shallow source material". [/quote]
So in short, your knowledge on the subject is superficial and shallow.