Derek Acorah

In 2007, after "ghosts" started appearing across Earth, Derek Acorah proclaimed on television, "Well, no-one needs me any more." (TV: Army of Ghosts)

Behind the scenes
Though not directly mentioned in the episode, in the real world, Acorah worked as a medium on shows such as Most Haunted at the time Army of Ghosts aired. The gag here was that as "ghosts" started appearing, this would have meant his job was now obsolete.