That all-too-important Oct. 31 date is creeping closer and closer on the calendar, and in spite of all of your best planning efforts, you're still costume-less. I've been there, my friend. Haven't we all? With mere days left to go before Halloween, it sounds like you're in dire need of some last-minute 2017 DIY Halloween costume ideas.Here is Halloween costume that you can make with stuff that's probably already in your house.It's a nerd.