For most of the series Mr. Garrison, whose first name is Herbert, was the third-grade elementary school teacher at South Park Elementary. In the fourth season he was fired, but he was later rehired as the kindergarten teacher. By the end of the sixth season he was promoted to the fourth grade after the death of Ms. Choksondik.
Mr. Garrison suffers from a wide variety of social problems, the most notable of which appears to be schizophrenia. Mr. Garrison constantly holds a puppet known as Mr. Hat who he uses as a sort of second, more aggressive personality. For a period in the third season Mr. Garrison "broke up" with Mr. Hat, and used a different, more subdued puppet named Mr. Twig. Upon moving up to fourth grade, he abandoned the puppet in favor of a human assistant, Mr. Slave.
Another source of problems for Mr. Garrison is his sexual identity. Though he often acts in a very cliched homosexual manner, for a long time Garrison could be seen chasing women, and displaying a very homophobic attitude towards gays. However, he would eventually have a change of heart, and "came out" as a homosexual in season 4. He continues to use homophobic language however, indicating that he still may have sexual issues that need to be resolved.