I understood the influence Joker has. Something that affects people, on an almost subconscious primal level. For most people--regular people--he inspires fear. For the less stable people--he simply inspires.
Dr. Byron Meredith, better known as Merrymaker, is a super-villain in DC Comics, as part of Batman's rogue gallery. Within the stories doctor Meredith was a former psychiatrist working at Arkham Asylum until he left due to his fascination towards the Joker's chaotic nature and how it subsequently affected those like-minded individuals. Adopting the moniker of "The Merrymaker", Meredith became an enemy towards Batman.
Dr. Byron Meredith was once a psychiatrist at Arkham Asylum who was considered infamous due to his violent ways when he was treating his patients. Bruce Wayne had met Dr. Meredith, in passing, while attending a gala dedicated for the Gotham psychiatric community. During their meeting the doctor boasted about how he understood the insane criminal mind better than anyone else. While most doctors often feared the madness of The Joker, Dr. Meredith, along with Dr. Harleen Quinzel were the only ones willing to take on the Clown Prince of Crime. Unlike Dr. Quinzel, who went mad with The Joker and became both his girlfriend and sidekick; Dr. Meredith decided to leave Arkham and open up private practices for the Joker obsessed, people trying to emulate Joker's behavior. Unbeknownst to any of his many patients, Dr. Meredith harbored no sympathy towards any of them, he merely took advantage of their alienated states of mind in order to make large amounts of money.
Soon after the Joker returned to Gotham following a year-long absence, Dr. Meredith managed to convince his patients that it would make the Joker proud if they were to caused chaos in Gotham. One of his more assertive patients, Dr. Philip Miles, happened to be a dentist, which proved to be very useful to his plans. Dr. Meredith had faked his own death and subsequently had Dr. Miles falsify the bodies dental records so that the death would seem legitimate. Now having fallen under the radar, Dr. Meredith dressed himself-up as the criminal known as and became the leader of the gang known as the League of Smiles and supplied the League's members with firearms he stole from Arkham. But it turned out that, Dr. Meredith was using the chaos as a diversion so he could kill people who had wronged him, such as his ex-wife and her lawyer. Merrymaker would send the League of Smiles to key locations in order to cause terror while Merrymaker would murder his targets, located nearby. However, while chasing down the Joker, Batman deduced that it was Byron Meredith who was controlling The League of Smiles's actions for his own goals. He catches the League about to raid the Gotham City Children's Hospital and leads them to the Merrymaker, just as he was about to murder his ex-wife. Batman reveals to them Merrymaker's plans, how he took advantage of them and how he would have eventually sent them on a suicide mission while he ran out on them. Having been enraged, The League of Smiles begin beating on Merrymaker for ten seconds until Batman subdues them.
Merrymaker is later sent for a psychiatric evaluation in order to determine his prison sentence. Dr. Meredith explains his intentions and plans to the psychiatrist and pleads to be sent to Blackgate Penitentiary, as apposed to Arkham Asylum, because he considered the asylum's inmates far to dangerous to handle. Unfortunately for Dr. Meredith, his psychiatrist happened to be a Joker obsessive himself, so he intentionally has Meredith diagnosed as insane and sent to Arkham, much to his horror.
Merrymaker has no real super human abilities; however he is a trained psychiatrist and an expert amoral manipulator.