It's strange how Fluttershy's become the most developed character on the show.

Really, Flutter Brutter is the best example. If that episode had aired earlier in the series, then it'd be about Zephyr taking advantage of Fluttershy while Rainbow tries to set him straight and help her. Instead of Flutters doing it for her parents.

I like to think of AJ and Pinkie's lack of development is because they are already where they want to be in life. Apple Jack taking care of her family, her farm, and her friends, and Pinkie Pie being… Pinkie Pie.