Zonker's family consists of his mother, father, "Uncle" Duke, his nephew Zipper, and his sister. His mother and father have a habit of fighting which leads to the mother leaving for a short time to clear her head (but always returning in time to water the plants). Whenever this happens, Zonker's father becomes upset and visits Zonker, within minutes of the argument. On one occasion, Zonker's mother never actually left. His father thought she did, however found her in the garden after calling his son for help. Zonker's sister never appears in the series, however is the mother of Zipper Harris. Zonker's ancestors from Colonial America are mentioned several times in the series. Nathan Harris was a minuteman (who could literally be ready in one minute) as well as an activist for civil rights and was responsible for "freeing" a nearby slave (the slave was under the impression that they were in Virginia, where slavery was still legal. They were, in fact, in Massachusetts, a free state). Nathan's wife, Amy Harris, was equally revolutionary, fighting for women's equality in the Constitution and taking up an apprenticeship with Paul Revere to become a silversmith. Neither cause worked out very well however, as men weren't interested in women's civil rights and she was unable to even cast simple pewter tankards. She quits her apprenticeship when Nathan assures her that he needs her as a companion and equal as well as a wife.
While at Walden Commune, Zonker spent most of his time watching TV, getting high, and swimming around in a small puddle (called "Walden Puddle"), which he considered to be a sacred and holy place. In his early years in the strip, Zonker had the ability to talk to plants. (Mike also talked to the plants during Zonker's stint as Lieutenant Governor of Samoa.) In later stories Zonker appeared to lose this ability, but it has sprung back up occasionally, and he has been seen conversing with a marijuana plant, and a scrawny Christmas tree in recent years. Other than these few exceptions, this power seems to have left him, and he misses it terribly. When wondering out loud why he had it in the first place, he was told "It was the drugs, man". Ironically, it was a plant that informed him of this.
Zonker is habitually unemployed, and is very protective of his slacker lifestyle. He has taken on temporary jobs as a bartender and a postman, but always leaves these careers as soon as he gets bored with them. The only "work" to which he has shown any diligence is acquiring a suntan. Throughout the 1980s he spent more and more of his time trying to develop "the perfect tan", and even became a celebrity (on par with a professional athlete) for his accomplishments, with George Hamilton as his idol. Eventually he wised up to the damage the sun was doing to his skin, and has since appeared in public service announcements about sun safety.
After his graduation from Walden, Zonker eventually enrolled in "The Baby Doc College of Physicians" (which was run by Uncle Duke; an old family friend). However, he dropped out after winning $23 million from a lottery ticket. Shortly afterward he had to spend most of it on saving Duke from being a zombified slave, but had enough left over to buy a British title (His Lordship the Viscount St. Austell-in-the-Moor Biggleswade-Brixham), which caused him to be called in to England as a tie-breaker for a vote in the House of Lords over one of Margaret Thatcher's tax bills. He stayed at another lord's castle for several months, oblivious to many not-so-subtle hints to leave, and was eventually forcefully removed by a butler. He ended up as a live-in nanny for Mike and J.J. Doonesbury (who kicked him out in the early 1990s).
Currently he is a live-in babysitter for B.D. and Boopsie's daughter Samantha in Connecticut. As they live on the former Walden Commune, Zonker has been reunited with his beloved puddle. He supports Samantha by working at McFriendly's, seemingly a portmanteau of McDonald's and Friendly's restaurants.
Occasionally he travels back to his birthplace of California to commune with "Old Surfer Dude", an elderly man who preaches the virtues of the surfer lifestyle in a style reminiscent of both a kung fu master and Yoda. He has been in conflict for many years with David Geffen for denying the public access to his beaches, in conflict with California law. Geffen finally gave in 2005.
Zonker is entirely uninterested in sex and romance and has never pursued a romantic relationship. He claims that this is because his heart was broken by a girl when he was ten years old, and that this convinced him that love wasn't worth the trouble.
There is an accessway in Malibu named after Zonker.
Wesleyan University students hold an unofficial yearly event in April called Zonker Harris Day, celebrating psychedelic music and culture, with the Doonesbury character as a mascot. In early 2008, the new Wesleyan University president, Michael Roth, declared Zonker Harris Day to be "stupid", and the Residential Life office officially opposed its "hippie-druggie" image. Funding for the event was banned pending a new title. After prolonged disagreement, students renamed the event "Ze Who Shall Not Be Named Day". With a new name, the former Zonker Harris Day was held as usual on April 19, 2008. The students continue to protest what they view to be unnecessary and irrelevant censorship, while the administration toes the line that Zonker Harris Day gives the University a poor image.