Whether you were just being lazy, didn't have plans until last minute or were just too busy to get a costume ahead of time, Inventor Spot's list of 15 easy last minute costumes can really help you put something together, many of them requiring nothing more than stuff you probably have around the house already. I'm a pretty big fan of this cactus costume, that requires nothing more than straws and a green sweat suit, but the umbrella bat is a pretty impressive costume for being made of things…