Hello! This is a general question (open to answers from anyone) about how to sew pants with a lining to make them poofy. Specifically, characters in Kingdom Hearts. I’ve been wanting to cosplay Ventus/Sora (KH2) but I’m not sure how to tackle the pants. Would I just sew a second layer of pants minus the fly/panel etc., then sew the leg ends together and then fill the pants with batting/foam and then finally sew the top/waist up? Idk how I would sew the zipper in though with the bat/foam in it.
Lining the shorts to create extra space for the poof is a good idea, as is stuffing it, especially if you want a very stylized and cartoony look. Batting would be a better option than foam for this, since it can more easily conform to the poof of the legs (and create the bit of heaviness seen at the bottom of the pants) without needing to go all the way up to the waistband, and without too much added thickness that isn’t as compressible. Another option, especially if you want more poofiness towards the bottom of the pant, is to gather long strips of tulle and sew them into the bottom hemline, between the shell and the lining. This is a technique often used to keep large puff sleeves poofy, and may help you here.
For the lining, I would recommend making it with a straighter leg than the outer pant, and then sewing the two together at the bottom. This will require shaping the outer pant leg so that it is a bit bulbous at the bottom, but then tapers quickly to match the lining. This will allow there to be some space between the shell and the lining, creating not only space for your stuffing, but will help the outer pants stay a bit poofy all on their own (and will allow for the visual heaviness of the more bulbous bottom of the pant). Try a few mockups at ½ scale, then scale it up to a full-sized mockup once you have a pattern that seems to work, and tweak from there to fit a human form.
As for attaching the zipper, it shouldn’t be much different from any other fly front pants, only you are going to insert the lining into the seam with the fly underlap on one side, and insert the zipper between the lining and shell on the other side. Here are a few tutorials to give you some ideas on how it can go together: 1 (button fly, but you would sub a zipper) 2 3 (needs a subscription, but you can get a free trial if you don’t have one).
Be sure that whatever you choose for your outer fabric, that it has enough structure on its own to help hold that shape.
I hope that helps! Good luck :]