There are reasons why The Great and Powerful Trixie chooses to wear an informal - and admittedly childish - cape which covers her flank. These reasons remained concealed...until now.
You are...you can't remember, so lets just go with Anon. You are Anon, and you have arrived upon Equestria as the result of a magical spell cast by Twilight Sparkle...your new roomate.
Several years down the line, Scootaloo is still earthbound and without a cutie mark. Feeling alienated, she looks for a new friend to hang around with. She finds the friend in the local dragon who has grown new wings.