Here's another really quick and easy DIY you can do right before Halloween. I haven't really had the time or energy this year to make an all-out costume like I normally do, but I still like to be at least a little festive. Good thing this project only requires a sweatshirt, some embroidery thread, and about five minutes.
Start by creating a straight line down the front middle of the sweatshirt. I made my stitches pretty big - about an inch long each - because I might remove the thread after Halloween. Then cut three or four strands of thread that are about a foot and a half long. Attach the first strand to the top left of your sweatshirt, string it through the middle line of thread, and attach it to the other side of the sweatshirt, making sure there's enough extra thread to hang down and look like ribs. Do the same a couple more times down the rest of the sweatshirt.