Callahan died Saturday at Good Samaritan Hospital in Portland, Ore., after undergoing surgery and treatment for a chronic bed sore, said Kevin Mullane, a longtime friend.
Paralyzed from the chest down in a car accident in 1972 at age 21 and a recovering alcoholic since he was 27, Callahan began selling cartoons in the early 1980s and went on to be internationally syndicated in newspapers and magazines.
Working on the premise that "anything in the world is fair game," he was known as an equal opportunity offender whose diverse targets included the disabled, the homeless, fat people, Alzheimer's patients, feminists and the French.
"He had a big following," said Deborah Levin, Callahan's former manager. "When he was published in the L.A. Times magazine, I received calls and letters [for him] from everyone from celebrities to prison inmates; It didn't matter. He spoke to all of us."
"I thought what was refreshing about him was, in an age of political correctness, he was bucking the system," said Bill Plympton, a two-time Oscar-nominated animator who first met Callahan in the late '70s when he showed up in his wheelchair at a cartoon class Plympton was teaching at Portland State University.
"He showed me his portfolio, and every cartoon was genius, a very wacky, crazy humor," Plympton said.
Although he could extend his fingers, Callahan could not close them around a pen. To draw his cartoons, he would wedge a pen between the fingers of his right hand. Then, with control coming from his shoulders, he would guide the pen with his left hand.
Among his better-known efforts:
Two Ku Klux Klansmen heading out at night in their white sheets. Says one: "Don't you love it when they're still warm from the dryer?"
A beggar in the street wearing a sign that reads, "Please help me. I am blind and black, but not musical."
A sign in the window of a small, street-side restaurant says: "The Anorexic Cafe, Now Closed 24 Hours a Day!!!"
An imposing woman glares at a small man and says: "This is a feminist bookstore! There is no humor section!"
A small boy and his father look at a dog lying on its back with a large shard of glass embedded in its chest. "How much is that window in the doggie?" asks the boy.
Callahan was not swayed by hate mail blasting him for being racist, sexist, ageist, sick, depraved and disgusting.
"I have newspapers calling me and telling me to watch out," he told the Tacoma News Tribune in 2004. But, he said, "If I put a governor on my muse, nothing will come through."
Callahan's cartoons dealing with the disabled were among his most controversial, including one in which the instructor at an aerobics class for quadriplegics says: "O.K., let's get those eyeballs moving."
"When you look at it, most people who object to my handicapped cartoons are themselves not handicapped," Callahan told the Chicago Tribune in 1994. "I get letters from other handicapped people who tell me, 'Go for the gold.' The handicapped enjoy that kind of humor. It breaks through the patronizing attitude the world has toward us. Frankly, we're tired of people walking on eggshells around us."
Offsetting the hate mail were letters from fans, including comedian Richard Pryor and Bill Clinton.
Humor columnist Dave Barry has called Callahan "living proof that a person can go through great adversity and pain and still — through a triumph of human spirit — be really weird."
Callahan's success as a cartoonist led to a string of books, including his 1989 autobiography, "Don't Worry, He Won't Get Far on Foot: The Autobiography of a Dangerous Man." He also created the animated TV shows "Pelswick" and "Quads."
Given up for adoption after he was born in Portland on Feb. 5, 1951, he was adopted as an infant by David and Rosemary Callahan and grew up in the Dalles, a town on the Columbia River, where his father managed a grain elevator.
Callahan began drawing caricatures while attending a Catholic school run by strict nuns. "I made fun of the nuns, mostly as a defense," he told the Chicago Tribune. He had his first drink when he was 12.
He was drinking heavily when he moved to the Los Angeles area in 1972. That July, after a day of drinking, he and a man he met at a party went bar-hopping. With his new drinking buddy behind the wheel of Callahan's Volkswagen Beetle, it crashed into a utility pole while traveling at 90 mph.
Callahan, who stopped drinking in 1978, curtailed his work as a cartoonist in recent years. Turning his attention to music, he wrote the songs and did the vocals on a 2006 CD called "Purple Winos in the Rain."
Callahan received a bachelor's degree in English from Portland State University after his accident and was enrolled in a master's degree program in counseling at the university at the time of his death.
"When he burned out on cartoons, he had to have something else to kind of get him excited," said his brother Tom. "He never sat still, no pun intended."
In addition to his brother Tom, he is survived by his mother, Rosemary; brothers Kip and Rich; and his sisters, Murph Callahan and Teri Duffy.