Hair clips

I noticed having watched this recently that the girls each wear hair clips throughout the film. Before their spells come true and they acquire more power, they have plastic, girly hair clips, then later on in the film they seem to upgrade to sparkly, more sophisticated clips.
I thought it was a nice touch. Why hair clips, I'm not sure, but in the first half of the film they look like cheap ones little girls wear. It's kind of cute though.