I recently watched the episode titled "The Girl Who Was Death", which features a mad scientist who thinks he's Napoleon. As I watched it, I found myself thinking about the old cliché of delusionally insane people thinking that they're Napoleon. It seems to pop up a lot in films, TV and other media of a certain age (Looney Tunes cartoons, for example), tapering off around the 1960s (though still making the occasional appearance, in things like Highlander sequels); and there even was a famous pop song referencing it. Nowadays, one doesn't hear about nuthouses full of Napoleons; more modern sufferers of delusions are apparently more likely to think they're Jesus; either that (I once heard) or superheroes or ninjas or such.
I imagine that this has to do with the historical figure of Napoleon having cast a much longer shadow earlier in this century than he does now. When Napoleon loomed large in the public consciousness, a padded cell probably looked a lot like Saint Helena. It wouldn't surprise me if the I-think-I'm-Napoleon cliché was an old Vaudeville device or similar, dating back well before World War 2 (which somewhat demoted the French emperor's standing in the league of scourges of Europe), and the mass-media-saturated post-war world (whose brighter, more vivid archetypes undoubtedly displaced 18th-century history books from the public consciousness).
The ever-shifting landscape of public image affects how we see things. For one, the villain in The Girl Who Was Death reminded me of none other than Xeni Jardin.