Celestia's hilarious awkward expression at the very end of S03E10 "Keep Calm and Flutter On".
I thought Celestia was going to be a nightmare to vector, but all in all, it took like three and a half hours. Thanks to =90Sigma for being just about the only person who seems to vector Celestia (and Luna) regularly. I had to look at some shots to get an idea what her tail was like because it's cut off in the reference image!
Anyone else get the feeling that Celestia's hair is the real her and that she wears her body like a sleeve the way that those strange plasma people did in that one star trek episode? And that her hair goes through her entire body and comes out her tail?