Trolling around the Internet last night, I happened upon a tutorial for a car litter bag. We normally keep a Wal-Mart bag on the floor of the back seat for that purpose, but that looks messy and is always in the way if we have more than one person in the back seat. The litter bag tutorial I found used brightly-patterned cotton fabric and had a pocket sewn on the front for tissues, or anything else you wanted to carry. I looked at my stash and saw an old pair of my wife's jeans, which I had…