Okay, it wouldn't be an underwear bag technically, it would be more along the lines of an undergarment bag.
With the completion of the Steampunk outfit, I find myself with a pair of pantaloons and three underskirts that I've made. Also Peaches and Cream Barbie's dress came with an underskirt as well. This leaves me with a considerable amount of undergarments.
Now right now my entire clothing collection is stuffed into Ziploc bags, it's not ideal, but it keeps things together, clean, and, easily assessable. It used to be a small amount of bags but now the categories are split into; Barbie Casuals 1, Barbie Casuals 2, Barbie Formal 1(Fairytale Princess), Barbie Formal 2 (Evening Gowns), Ken, Momoko and Smaller dolls, and Coats. Coats are in a smaller bag, since there's less of them. Also Chatty Cathy's clothes are in a separate box that is stored on their shelf. And Cindy Sad Eyes has a cigar box to store her stuff, although she has a lot less than everyone else.
Now do you think I should make a new bag for these items? Honestly I leaning towards thinking I should since they really don't fit in any category that I already have. Also this way I can put the doll underwear I have in there too. Honestly I won't be using these clothes think I should since they are a bit of a specialized product. I just don't want a bunch of smaller bags. Sigh, all in a days work I guess.