It's a phenomenon I've noticed over the years of babysitting in families that happened to be mostly female, but for many young girls, including myself, your "favorite Disney Princess" often becomes a part of your identity.
I've noticed this mostly in families with multiple sisters. For myself growing up, my favorite Princess was always Belle, and my sister's two favorites were Cinderella and Jasmine. It makes it easier for adults who bought us Christmas presents-they could buy us the same thing, like a hairbrush or toy, but make it unique for each of us by buying us each the version with the face of our favorite Princess plastered over the front.
I've mentioned these girls before, but in one family, in games of pretend we each assumed the roles of our token favorite Princesses-Cinderella, Ariel, and myself as Belle. But rather than waiting around to be rescued by our Princesses, most days we went on various adventures rescuing our Princes from our movie's villains.
For years now, my friend Christy has referred to my sister and her husband as Cinderella and Prince Charming, ever since seeing my sister in her wedding dress. Poor Tony now has the unfortunate title of "Beast" (I try to add that he's the transformed Prince, but the Beast is the enduring image of Belle's other half. Sorry, Tony :) ).
Of course, many people think this phenomenon is potentially dangerous for young girls, and all I'll say in this post is that it's a complex issue.
Have you found, in your experience, that children do the same thing? How do you think it affects their play and sense of identity?