Although not technically a costume, I feel the following vehicle qualifies as fodder for Bad Costume Wednesday:
For those of you scoring at home, that's an invisible submarine tank crawler. Because sometimes you want to be underwater, and sometimes you want to crawl along the ground, you always want to be invisible. Except for the bits inside, but come on, who is going to see you in your big scary black robe or, in the case of Wonder Woman, with your breasts barely contained in shiny red, blue, and gold, right?
Just because you can make it invisible, doesn't make ugly go away.*
(From "America's Greatest Comics" number 1, 1941.)
* This motto coming soon to an After School Special near you!