Moving on from fancy dress balls, here are a pair of cotillion figures which actually involve some degree of costuming, at least for loose definitions of the concept. Both figures are taken from H. Layton Walker's Twentieth Century Cotillion Figures (Two Step Publishing Company, Buffalo, New York, 1912), source of an endless supply of delightfully weird figures. There are actually Halloween-themed figures in Walker's book, but they're quite dull by comparison with these two!
Both figures are simple mixers, with either the ladies or the gentlemen selecting partners from a group of opposite-sex dancers. Dozens of figures of this sort were published over the years, but these two take the concept to a whole new level by having the dancers put on some sort of silly costume during the ball itself, presumably right over their normal evening dress.
You wouldn't actually want to use figures like these at a fancy dress ball, where the dancers are already in masquerade-type costumes, but they would add some interesting variety at a ball or cotillion evening with dancers in normal 1910s eveningwear.
I'll give the original text of each figure. First, some silliness for the gentlemen:
For this figure six large paper sacks with fruit painted on the front of each are required for gentlemen, who step into an adjoining room and draw them over their heads. The ladies receive six tags having on each the name of the fruit on the sacks. The gentlemen, when called by the leader, march into the room in single file and the ladies select their partners according to the names on their tags. The gentlemen will tear their sacks and dance in this costume.
The costume element here is not very elaborate, just pictures painted on paper bags, but I think the initial direction to "draw them over their heads" is a bit misleading. Look at the last line: they dance in "this costume". I don't think these are small paper bags that just fit over the gentlemen's heads. I'm not even sure they hide the gentlemen's faces, since there is no need for them to be anonymous. The choosing was done when the ladies received the tags with the names of the fruit.
I think that these are actually full-body-sized paper sacks, perhaps with holes for the gentlemen's heads to stick out so they can see where they are going when marching back into the ballroom. The tearing at the end would be the gentlemen getting their arms free so they can hold their partners properly. The idea of gentlemen with sacks (with pictures of fruit) over their heads is funny, but the idea of gentlemen in full-length giant paper sacks covering their bodies with just their arms and heads sticking out is even better. It's more work to create the bags, but I think it would be worth it!
Now, just in case anyone doubts the idea of making full-body-size costumes for a cotillion, let me introduce you to the Stocking Auction! In this figure the ladies are the ones with the sillier role. That's a little more unusual in a cotillion figure, but this is, after all, the twentieth century. Women's suffrage is on the horizon, so why not extend such egalitarianism to ballroom games?
Here's the original language:
Ten young ladies are called up and taken into an adjoining room. They are then persuaded to step into enormous stockings made of different goods, one a silk stocking, one a brilliant golf hose, another a plain stout yarn affair, the fourth an old white stocking with pink toe, the fifth a baby's sock, the sixth shows wonderful clocks, the seventh a clown's stocking, eighth an open-work bas de soie, the ninth a blue stocking, and tenth an old stocking patched and worn. Then the auctioneer taps his hammer and the bidding starts. After the bidding is over, the bags are opened (or stockings are opened) and the men who bid the highest dance with their ladies.
Sexual politics aside, this figure would never have worked in the nineteenth century, with its bulkier ladies' fashions. But by the early 1910s, the silhouette is slender enough (think Titanic) that ladies could presumably manage to wriggle into giant stockings. Note that the ladies must be able to walk, and, unlike the fruit-sack gentlemen, must be anonymous, so the gentlemen don't know whom they are bidding on. That means covering both faces and gowns. So the stockings need to be pulled over the head, not stepped into as if preparing for a sack race. The toe of the stocking would be at head level and the thigh part of the stocking would fall somewhere around the ladies' ankles, so that their faces are covered but their feet are still free.
Also note that these are not paper sacks; they are made of "different goods", meaning yard goods, actual textiles. This might actually be easier for the prop-makers to construct than giant paper bags, since one could simply cut out fabric in the right shape and sew up the seams, leaving some way to open them up to gracefully reveal the ladies, or at least for them to get their arms and faces free. It's possible that the ladies step entirely out of the stockings for the dance part, but I think it would be much funnier to have them stay in, with just their faces peeking out!
For both figures, the general pattern would be that a group of couples are selected and dance with each other, then separate so that half of them can get into costume, then have the selection of new partners (the ladies drawing fruit cards or the men conducting an auction) and the matching up, ending with more dancing.
The Stocking Auction could be rather time-consuming, so keep in mind that it should be done as quickly and entertainingly as possible, perhaps with amusing descriptions of the available stockings and over-the-top enthusiasm among the bidders. It could either involve a relatively small selection of dancers (so it goes quickly) or as many couples as possible so that everyone gets to be involved. The limiting factor is probably how many giant stockings the hosts can come up with! By the late nineteenth century there were merchants specializing in both fancy dress costumes and props for cotillions, just as today there are costume rental shops and party supply stores. It's fun to imagine that the range of props available for purchase included giant paper bags and/or human-body-sized stockings in various fabrics, but I suspect these were the sort of thing that had to be manufactured at home.