"You'll be popular--
just not quite as popular
This adorable pink party frock is worn by Galinda when she goes to the ball at the Ozdust Ballroom, accompanied by Fiyero. She tricks Elphaba into wearing a horrible hat (that ends up being her iconic witch's hat), ends up getting accepted into Madame Morrible's Sorcery Seminar, and makes friends with Elphaba. She also sings the famous song, "Popular".
The dress, like all of Galinda's costumes except the One Short Day dress, is in two parts--the skirt and the top. The top has an empire bodice, pointed waist, and a fluffy skirt that, in the words of Dianne Pilkington, "moves beautifully".
It started out as a baby blue in the San Francisco previews, as seen below:
But changed to a bright pink in later incarnations. The colours below kind of vary due to the photo quality, but it's also possible the colour changes slightly depending on the actress portraying Glinda--you'll notice the blonde wig she wears (as well as the hairstyle) changes from production to production to be flattering against her skin.
The middle part of the bodice is divided into 12 panels (where the seams are). The underfabric is a pale pink, and ribbons go diagonally--see below.
There is a zipper closure on the top, and I have no idea about the skirt... probably zipper as well. It looks like there's a seam in the middle back of the skirt.
The skirt is what modcloth calls a "strata" skirt. The layers are pleated sheer fabric with pink ribbon stripes and pink ribbon trim.
Accessories: she carries her adorable purse
and wears some sparkly shoes
And has an unknown type of pink flower pinned in her hair, which she transfers to Elphaba during "Popular"
Bodice (view B) It's not empire waisted, but it's a good basic pattern.