Gary has a reasonably large family, consisting of two parents, two younger siblings, and two older siblings. They all share his optimistic, fun-loving personality, and are always doing something together.
Mr. and Mrs. Harrison's names are Phil and Karen. Phil has blond hair like his son, and wears a yellowy-orange collared shirt, a wine-red jacket, and dark blue jeans. Karen has shiny red hair, and wears a pink shirt with a turquoise vest overtop, and a sea-green skirt. She also wears turquoise earrings. They both enjoy reading to their kids about the Mormon prophet, Joseph Smith. They convinced Randy Marsh to convert his family to Mormonism, even though he had originally intended on telling them off for teaching his son about the religion (he had been worried that Stan would try to convert to it).
Their names are Mark and Jennifer (Jenny). Mark also has blond hair, and wears an orangy-yellow sweater and light blue jeans. Jenny has orange hair, and wears a lilac shirt with a blue vest overtop, and a short, turquoise skirt. Jenny tried to befriend Shelly Marsh by saying she was lucky to have a nice little brother like Stan, but Shelly merely said that she thought Stan was stupid and ignored Jenny the rest of the night.
Their names are David (Dave) and Amanda. Dave has orange hair, like Jennifer, and wears blue overalls over a white shirt with buttons. Amanda is a baby, and wears pink pajamas and a pink hairclip. Curiously enough, she is the only known family member with brown hair. She is probably around a year and a half or two years of age, as she is able to talk.
When Gary was first introduced, his upbeat personality caused him to be considered lame to the other boys. They told Stan to "kick Gary's ass", but when Stan tried to do so, he ended up conversing with Gary instead, and decided that he was cool. Gary and Stan then started hanging out together, though Stan became a little reluctant to participate in this developing aquaintance, as the other boys (notably Cartman) began teasing him for "being in love". Finally, after hearing the story of "The Book of Mormon", Stan decided that Mormonism was all based on a pile of lies, and he then told his friends that he didn't want to hang out with him any more. Gary came over to the boys at the bus-stop the next day, and told Stan he didn't have to worry about being bothered by him any longer, but finished with a very thoughtful speech about how proud he is to be Mormon and what it has done for him, even if he is aware of inaccuracies. The speech ended with: "All I ever did was try to be your friend, Stan. But you were so high and mighty that you couldn't just look past my religion and be my friend back. You've got a lot of growing up to do. Suck my balls." upon which he turned and walked away. Cartman decided that Gary was cool after all.
Other than some scattered cameos, Gary hasn't been seen since this episode; nor has his family. One might assume that Gary didn't want to be in a class with people who were going to discriminate him because of his religion, and so either moved away, or took up home-school.
Gary is currently in a relationship with Janet Testaburger after noticing she didn't care if he was mormon. After Wendy found out, she told Stan to go beat him up, but Gary wins. Stan realizes that he should allow Gary to be happy.