Check out Kal-El's DIY astronaut costume! And I didn't sew a stitch!
I started with a $7 Hanes sweatsuit. I printed the NASA badges on my printer from images I found online, laminated them and applied them with Badge Magic. The "helmet" is, of course, the hood plus one piece of laminating film (after it has gone through the machine) attached to the inside of the hood with adhesive velcro.
The stripes on the pants are done with black duct tape. The straps on the backpack are made from black duct tape two. I stuck two pieces to one another with the adhesive sides facing one another so it wouldn't be sticky. They are stuck to the oxygen tanks with more duct tape.
The oxygen tanks are two two-liter bottles covered in silver duct tape with a piece of hose attached. We had extra in the basement. It's the kind you would attach to your furnace to direct the condensation discharge or that you would use on a pond pump.
Extra bonus? There is plenty room underneath to layer a couple shirts and an additional sweatshirt plus long-underwear which you need in our climate to trick-or-treat at the end of October without wearing a coat over your costume. Oh...the number of years I cried as a kid because I had to cover my costume with a coat or wear it underneath and look like the Goodyear Blimp.
Sweatsuits are my favorite way to create a quick costume. In the past I've also done a skunk and a squirrel: