Simplicity 2252 en route to being Elsa Schraeder's ballgown.
As you can (maybe) see, we're adding straps to it. Also, if I take out the basting on those midriff folds, they all fall out due to the extreme drape-ability of the satin , so that's a little awkward; I guess if I cared deeply I'd put some interfacing in it. But, hey, it's only worn in one scene in a 2-performance musical, so not worth getting too excited about.
Still to come: the bodice lining (we've decided to not bother with the boning -- again, it's not like it's a "real" dress) and some sort of hem (probably just narrow serging). And, obviously, ironing, since hung up like this you can see all sorts of wrinkles. And some sort of blob of tulle up at the neckline, like the movie version.
Overall, this is a fun pattern.