Alter-egos are in vogue. There is the introverted, family-man Waiter White who is also the meth-dealing drug baron Heisenberg. Dexter Morgan, the Miami-based blood-spatter analyst is a viligilante-killer of those who pass through his lab and in his eyes escape justice. Donald Draper from Mad Men has a dark, but not bloody past in his mysterious true identity as Dick Whitman. However these television doppelgangers are prefigured (and later paralleled in film) by the comic book clamour of secret lives and dark secrets that arose in the 1930s with Superman and Batman, and reappeared in the 1960s with The Hulk and Spider-Man. There are recurring themes with all of these creations. Split identities, secrets to hide, heroism and difficult pasts which all make them who they are. Why are these alter-egos so engaging? What makes them the same, and how do they function differently. More intriguingly, why do these cultural phenomenons appear to be popular in batches? The popular fascination with the duality of human nature is most notably associated with Victorian novelists. The Strange Case of Dr. Jekyll and Mr. Hyde and Frankenstein sparked the supernatural imagination and lead readers to consider their own natures. In the case of Stevensons novel, it was thought to be inspired by the rumours surrounding Jack the Ripper, where the fathomless evil of such a man surely initiated the idea that he may walk among ordinary Londoners. How can such darkness be hidden? To return to the 21st Century, there are shades of alter-ego, with the purpose of each being nuisances to create an individual (as it were) creation at each turn. Where do the true identities lie, if indeed they are separable? Read on to find your favourites. Comments a warmly welcome, unless I flip out and get angry. You don't want to make me angry...