go away seb

True, but Pinkie has an alter ego or sorts, and because it was her personality when she lived at the rock farm, it shares the name she went by on the rock farm (i.e. Pinkamena).

The name Pinkamena is used to identify her alter ego while Pinkie is used to identify her current self. That sort of thing has been used before (incoming Kamen Rider Den-O example):

http://ic.pics.livejournal.com/sennetari/9868143/50441/50441_320.jpg Yuuto

http://images.cosplay.com/i/costumes/200/220169.jpg Sakurai

Both the young and old version are the same Yuuto Sakurai but they've used the first namee for the young and last name for the old one.