Impostor Mad Hatter

He looks nothing like the Lewis Carroll character.

I mentioned there was a second Mad Hatter. He is more about him.
History
The real Mad Hatter villain made one appearance prior this impostor. The impostor was a thief with a hat collection. He was obsessed with completing his collection, which often led him to steal headgear. He attempted to steal Batman's cowl for his collection. After several failed tries, he sprayed the cowl with a toxic and radioactive substance thus forcing the cowl off. He stole the cowl, but Batman and Robin tracked it via a Geiger counter. He claimed he went straight, but this was revealed to be a lie. The real Mad Hatter returned and said he killed the impostor. This is revealed to be a lie and the impostor returned. He was seen in Arkham Asylum despite not being insane and was making paper hat. His moniker was retroactively changed to "Hatman".
Powers and Abilities
Like most Batman villains, he has no powers. He used various weapons he hid in his hats. He is also suppose to be sane, but is seen the Arkham Asylum.
References:
http://batman.wikia.com/wiki/Impostor_Mad_Hatter
http://en.wikipedia.org/wiki/Mad_Hatter_(comics)