There is so much awesomeness in this photo that your monitor may incur damage trying to display it. Brian Carr is a balloon artist and brony. This costume of Princess Twilight Sparkle in full regalia consists primarily of balloons that he carefully wove together.
His friend Eric Bennett (AKA Rainbro) is the lucky fellow who got to wear the costume at the Holiday Matsuri Convention in Lake Buena Vista, Florida.
I am not so fortunate to have a proper brony costume. But recently, my wife gave me a Rainbow Dash necktie. I plan to wear it to a couple business meetings in January.