I think Cupcakes was one of the most well written fanfics. The author did a great job with Pinkie Pie's character, especially considering what se was doing. Most fanfic writers couldn't even keep her in character if she was throwing a party.
Yeah, the author really captured her personality, especially with that "I'm Rarity" bit.
I could totally see her doing something like that.
...with a scarf, not intestines, of course.
IMO that's how you make horror fics even scarier.
When you don't capture the personalities of the characfers, they're just empty shells, which you couldn't care less about. When you manage to keep personalities intact, it toys with the reader with a kind of, "Yes, it really is THIS character doing this horrible thing. This one. The one that you've loved this whole time."