Jervis Tetch had been obsessed from an early age with Alice's Adventures in Wonderland and its sequel, Through the Looking-Glass. Eventually growing to believe he was the embodiment of the fictional Mad Hatter character, Tech combined his love of Lewis Carroll with an equally obsessive devotion to hats.
Tetch’s personality has been described by his doctors as acute manic-depression. When agitated or afraid, Tetch begins to rhyme as a defense mechanism, further reinforcing his resemblance to the fictional Mad Hatter. Allegations of pedophilia have also surrounded Tetch, who frequently involves children in his crimes.
Tetch began his criminal career at a young age; using his mind control devices to murder the entire Gotham Hawks high school baseball team. His first professional crime as the Mad Hatter saw Tetch robbing Gotham’s high society, before being foiled by Batman and sent to Arkham Asylum.
Mad Hatter would eventually escape from Arkham and assemble a small gang of followers. Kidnapping Lucius Fox, CEO of Wayne Enterprises and personal friend of Bruce Wayne, Tetch attempted to copy the information from Fox’s brain to create more sophisticated mind control devices. Thankfully, his plan was foiled by The Dark Knight and Mad Hatter was sent back to Arkham.
Tetch is freed from Arkham when Bane, in an attempt to overrun Batman with a plethora of villains, breaks the walls of the asylum and frees a large portion of the Rogue’s Gallery. He continues his reign of terror, eventually becoming involved with the Great White Shark in framing Harvey Dent for murder during Batman’s one year absence from Gotham City.
The Adventures of Batman & Robin
Tetch appears as a boss controlling an army of mechanical rabbits. He inhabits a virtual reality world filled with psychedelic imagery. His appearance in the game is based on his Batman: The Animated Series incarnation.
LEGO Batman: The Videogame
Mad Hatter appears as a playable character. He is able to double jump utilizing a propeller built into his hat.
Batman: Arkham Asylum
During his adventures in the Botanical Garden, Batman can find a tea setting hidden in the shrubbery. Examining the china unlocks the Mad Hatter’s biography.
Batman: Arkham City
In Batman: Arkham City the Mad Hatter is somehow able to psychologically trick Batman into thinking that Alfred has dropped the cure to the chemical that's killing him in the west of Arkham City. However, this "cure" is actually a syringe filled with an anaesthetic. The Hatter takes Batman to his hideout within Akrham City where he is staging a tea party with some of the other inmates. After a brief dialogue he attempts to take control of Batman with a hat that bears the features of a rabbit. Batman struggles and in the next scene is either seeing himself standing on a clock, suspended in space with the Hatter and inmates attacking him, or the scene is being shown to the player as a metaphor for his mental struggle.
After taking down the Hatter in this fantasy, perspective switches back to the Hatter's hideout where all the guests are sitting knocked out and Batman removes his hat and defeats the Hatter. Should he return to this room Batman will find the Mad Hatter crying and if the player engages the Hatter in dialogue, Batman will tell the Hatter to never get inside his head again, to which the Hatter replies that he "can't win" without Batman. Batman replies saying "then you lose".