Not to mention they remember stuff from their life as a caterpillar. Unfortunately they did this by causing them pain whenever a certain sound/scent was released. And when that sound/scent (i can't remember which it was) was given to the caterpillars that had now transformed to butterflies, the butterflies freaked out.
Dude they turn themselves into goop, turn into these magnificent winged marvels and they remember.... all of it. Weirds me out.