Proudest accomplishment: The wig, for sure.
I bought a "Blue Steel" wig from Arda Wigs, plus the Royal Blue wefts to sew in. I put off doing anything with it for too long because I was afraid of ruining the wig, then the next thing I knew, it was a week and a half before the con! 8D;;; My mom was the one who sewed all the wefts in, but it really was a team effort (I parted the wig hair, measured and cut the wefts, and held the wig hair back while my mom hand-sewed.)
We ended up running out of pre-made wefts, but luckily we were able to make our own out of the excess hair I had cut off.
This is the first time I was still working on a costume the day we left for the con. XD; I was still cutting and razoring the wig after midnight on the Friday morning of the con. XD

Other costume pieces:
Ears and horn are from Yaya Han
Glasses and tutu are from Party City
Necklace and black speakerbag I bought from LittleBlackBag.com (but they are no longer available sadly. D: ). Bag is by Fydelity
Headphones are from Coconuts (Spray Loud! brand)
Tank top, leggings, and shoes I've had for a long time