3. Heart Of Ice
As well as giving definitive versions of old favourites (the Joker) and creating their own new favourites (Harley), a strength of the series was to take B list villains and make them worth their salt as characters. While across the show there were terrific renditions of such silly-sounding supervillains as Clayface, the Mad Hatter and Scarface (the mob boss who happens to be a ventriloquist's dummy), the series' treatment of Mr Freeze was the standout, taking him from the bargain bin of Batman villains and making him a compelling, tragic figure. Once gifted scientist Dr Victor Fries, Freeze was trying to find a cure for his wife Nora's fatal disease when an accident caused him to be submerged in a freezing formula which made him cold-blooded - and cold-hearted. The same origin story was later used in Batman & Robin, although sadly Arnold Schwarzenegger's version lacked the depth of the animated character (ironic, isn't it?).