Number None is the most elusive super villain ever and is apparently invisible. As Mr. Nobody said, Number None is every nuisance that happens to you that you didn't expect. Number None seems to be able to transform itself into anything that can get in your way and is invisible until he does so.
He joined Mr. Nobody's second Brotherhood of Dada. He manifest himself 3 times: 1) The door that hit Agent !, while closing itself. 2) The banana peel that Crazy Jane slipped on. 3) The step that was crush under John Dandy's feet.
Its unknown if John Dandy killed Number None, because it unknown if it can be killed.