Today's villain is the Mad Hatter.
Usually dismissed as a lesser, goofier foe, Jervis Tetch, the Mad Hatter, was introduced in Batman #49 in 1948, created by Bob Kane and Bill Finger. His origin suggests he is some sort of scientist, but does not use a Dr. title in front of his name, unlike other villains in Gotham with scientific backgrounds. He has an obsession with hats, and, more importantly, with Alice's Adventures in Wonderland. This is the first of many villains to turn up in Gotham with Wonderland themes. This one-time appearance would be his last until 1987.
There is also a period during the campy 50's and 60's where a different Mad Hatter appears, created by Bill Finger and Sheldon Moldoff. This hatter does not appear to have a Wonderland theme, and over emphasizes his obsession for hats. Like all campy villains from this era, he has hat themed weapons, heists, and bad puns. Recently, this character has been renamed Hatman, and may or may not have been killed by the original Mad Hatter. Let's just all agree to forget this ever happened.
Most of this character's publishing history has been pretty dull and uninspiring. Having been regulated to minor villain status, he usually pops up in a group of villains and is easily dispatched by the Batman. He has a cameo appearance in the Long Halloween, where he is paired up with the Scarecrow, and spends his on-panel time feuding with his partner through nursery rhymes.
Lately, The Mad Hatter has started to evolve into something more sinister. He becomes specialized in mind-control, and is often hired by other villains for that purpose.
There have always been links between the Mad Hatter and children as far back as his reemergence in the late 80's. He has kidnapped multiple young girls in order to mind-control them to be Alice. This of course, leads many writers recently to hint that he is, in fact, a pedophile.
There are so many villains who, after all their obsessions and themes are stripped away, are nothing but burglars, or crooks. The Mad Hatter could have been written off as just another in the long list of crazy themed criminals who design robberies around their stupid obsessions. This extra dark element, an obsession with young girls, gives Batman a different evil to confront, aside from thieves and murderers. DC Comics hasn't really gone to this place before with their villains, and it makes this character far more horrific, and far less of a joke.