Okay, this is awesome. The translation of Nightmare Moon's imposing presence into Pinkie's upbeat and bouncy appearance gives her this feeling of...well, I guess the best word would be confidence and determination. She knows she has power, and she intends to use it.
On the other hand, this is obviously Nightmare Moon starting a disguise. No way would Pinkie take anything way too seriously. ...Nightmare Moon in Pinkie's colors. JEEZ