The Hypnotist is both a teacher and a hypnotist. He taught at the Santa School where Homer was trained to be a mall santa.
In his first appearance the Santa School he actually did not use hypnosis, but rather he teaches the wanna-be Santas. He later appeared as a hypnotist when he was hired by Mr. Burns to hypnotize the Springfield Nuclear Power Plant softball team and convince them that they are good players.
He tells the players, "You will give 110 percent." They respond, "That's impossible. No one can give more than one hundred percent. By definition that is the most anyone can give."
He also incorrectly hypnotized Roger Clemens into thinking he was a chicken. When Mr. Burns threatened to report him he simply hypnotized him into believing he did a good job.