It's not new, and it's not genius, but it's what I did and it worked out perfectly, so I'm sharing.
Spider Costume for 3 year old
Need*Black pair of sweats
*Black adult microfiber tights
(light weight, and they end up being the right length)I had a pair lying around that had a hold in the toe, no good to me, perfect for this.*Crochet cotton size 10 in black preferrably
*8 plastic grocery bags
Take tights and cut them in half at the crotch to waist band
With each separate leg: Serge (with cutter) halfway up the leg to close off the top part (part with the crotch part) and cut into two pieces (leaving the lower toe piece open ended.
Then serge the two parts with the crotch part closed so it makes them into tubes
Put the tube on your arm inside out, grab two plastic bags in your tube covered hand and pull the tights down over them.
Tada! stuffed, just enough, not too heavy.
Then about 2-3 inches from the armpit on the sweater sew the open end of the tube to or into the seam line (I just did it on top since I was in a hurry and it looks fine)
Do the same on the other side on the other arm, it's nice to make sure they are even side to side though.
The pair of sweat pants we had had pockets so I sewed the lower set of legs onto the back side of the pocket opening, leaving the pocket open access.
The legs will flop so grab about 20 inches of crochet cotton in black and thread on a needle tie a double knot and starting on the inside seam of the sleeve go out and catch the fake leg leaving about 3 inches of exposed string, sew and knot a few times to the fake leg that hangs below it. Knot it and cut. Do the same on the other sleeve and fake leg. Using a double knotted thread again sew the lower sweater fake leg to the fake legs on the pants, do on both sides. This moves the legs together-ish and keeps them semi-up. Only leave a few inches of thread between the legs.
All told, it took about an hour, and that was with having to re thread the serger because I ran out of thread, cinching up the waistband on the sweats and other such things.
Zurich was afraid of his costume at first. But after watching a Halloween Super Why episode, me putting on my Fantasia hat and me telling him that he had to wear his spider to go to Olea's school he put it on, tested it out and then said, "I lobe it Mom!"
and later "Can I walk like a spider?"
Sure, kid, break a leg, you got plenty.