If you feel you need to put on a costume to disguise what you are, doesn't that suggest that you are the scary thing you're trying to cover up? I think of the wolf in sheep's clothing.
The image of wolf in sheep's clothing comes from in the Sermon on the Mount. Jesus said: "Beware of false prophets, who come to you in sheep’s clothing, but inwardly they are ravening wolves."
From the WaPo article: