Jonathan Winters, the rotund, rubber-faced, squinty-eyed master of impressions and improvisational comedy who became a staple of late-night television for decades and was a mentor to Robin Williams and an inspiration for performers as varied as Steve Martin, Jim Carrey and Jimmy Kimmel, died April 11 at his home in Montecito, Calif. He was 87.

In a career spanning more than six decades, Mr. Winters received some of the highest honors of his profession and appeared in dozens of movies and television programs in addition to his work on the comedy circuit. He was known to start his stage shows by commanding an applauding audience that had risen to its feet, “Please remain standing throughout the evening.”

Yet it was less the punch line he savored than immersing himself in a far-ranging series of characters: hillbillies, arrogant city slickers, nerve-shattered airline pilots trying to hide their fear, a hungry cat eyeing a mouse, the oldest living airline stewardess.

“I was fighting for the fact that you could be funny without telling jokes,” he told the New York Times, adding that he thought of himself foremost as a writer and less as a stand-up comedian. He said he idolized writers with a gift for humor and singled out the sophisticated absurdity of James Thurber as an influence.

Two of his most memorable characters — cranky granny Maude Frickert and bumpkin farmer Elwood P. Suggins (“I think eggs 24 hours a day”) — were born from his early television routines.

“Nobody was safe,” said Gerald Nachman, an entertainment journalist and author. “He dug ruthlessly into American archetypes: disgruntled westerners, judgmental Martians, little old ladies, nosy gas station attendants. It was risky, but he did it so well. It became a commentary on Americans, and no other comedian could pull it off.”

Williams once told Playboy why Mr. Winters inspired him. “It was like seeing a guy behind a mask, and you could see that his characters were a great way for him to talk about painful stuff,” he said. “I found out later that they are people he knows — his mother, his aunt. He’s an artist who also paints with words. He paints these people that he sees.”

The death was announced on Mr. Winters’s Web site, The cause was not disclosed.

Onstage and off, Mr. Winters was wildly unpredictable. He struggled with bipolar disorder and nervous breakdowns. One of the most damaging episodes came in 1959, when he was reported to have climbed the mast of a moored historic ship in San Francisco while drunk and naked; he was subsequently transported to a sanatorium.

Mr. Winters was often viewed by producers as a liability, and this led to a scattershot, though memorable film career.

In Stanley Kramer’s all-star romp “It’s a Mad, Mad, Mad, Mad World” (1963), Mr. Winters played a moving-van driver. In the Cold War comedy “The Russians Are Coming, the Russians Are Coming” (1966), he portrayed a less-than-able assistant to a Nantucket police chief.

In “The Loved One” (1965), based on Evelyn Waugh’s dark satire on Southern California, Mr. Winters played two brothers, one of whom schemes to make room in his cemetery by launching corpses into outer space under the slogan “Resurrection Now!”

On television, Mr. Winters’s self-titled variety show aired on NBC from 1956 to 1957 and displayed him in dazzling form as a sketch comic. In one episode, he lampooned newsman Edward R. Murrow, conducting an earnest interview with Napoleon (he played both roles). In other spots, he portrayed Robin Hood and Gen. George Armstrong Custer.

His second show aired on CBS from 1967 to 1969, with Mr. Winters, in his signature characters, bantering with celebrity guests. Among them was Jack Paar, who had helped jump-start Mr. Winters’s career by hosting him on his own show years earlier.

In 1964, Mr. Winters asked the audience of “The Jack Paar Show” whether they ever undressed in front of a dog. Once the laughter died down, he added: “You think about that for a minute. A bird somehow doesn’t count. Or a cat. But a dog.” Pause. “They really stare.”

In another appearance with Paar, Mr. Winters was handed a long stick and asked to improvise. As he held it, he started making the clicking noise of a fishing reel.

“Well, that was a pretty good cast, wasn’t it Bob?” he said to an imaginary friend. “I think we’re on to something.”

Then, he looked into the distance and tugged at the pretend fishing rod. “I’m sorry, Margaret,” he said, “try to swim in.”

Perhaps his best-known work in television was playing Mearth, the half-earthling, half-alien son of the title characters in the ABC sci-fi sitcom “Mork & Mindy,” which starred Robin Williams as Mork, an alien from the planet Ork, and Pam Dawber as his earthling girlfriend, Mindy, who became Mork’s wife.

Williams, who had grown up idolizing Mr. Winters, smoothed the way for him to join the cast in 1981, the fourth and final season. Mr. Winters gladly took on the character of Mearth, who hatched from an egg middle aged and weighing 225 pounds — explained by the fact that Orkans age in reverse. Clad in bright red overalls holding a frog in the pocket, and with his plump frame and curiously furrowing brow, Mr. Winters made a seamless transition into the role of a big, cuddly baby.

Jonathan Harshman Winters III was born Nov. 11, 1925, in Dayton, Ohio. His father, an investment banker, was an alcoholic. He said his father once locked him in the car for hours while getting drunk at a bar.

He was 7 when his parents divorced. His upbringing with his mother was equally unpleasant. She became a talk-show radio host, and he described her as increasingly jealous of his success.

He once brought his mother on “The Jack Paar Show” in the hope she would enjoy it. “Jack said, ‘You’ve got a hell of a talent here, you must be very proud,’ ” Mr. Winters recalled. “And my mother said, ‘He’s the biggest joke I ever wrote.’ ”

At 17, he dropped out of boarding school and joined the Marine Corps. After World War II service in the Pacific, he entered Kenyon College in Ohio, where he said he stayed for about “an hour and a half,” before enrolling in the Dayton Art Institute. (He later received critical praise for his paintings.)

In 1948, he married a fellow art student, Eileen Schauder. About that time, he won a talent contest that led to a job at a Dayton radio station. He was fired after a year for conducting interviews with himself in strange voices.

In 1953, Mr. Winters moved to New York and began appearing in commercials and television programs. He polished his array of wacky-sounding noises (the cackling laughter of drunk grandparents, the mumbling of farm workers).

His wife died in 2009. Survivors include two children, Lucinda Winters and Jay Winters; and five grandchildren.

His book of short stories, “Winters’ Tales” (1988), made the bestseller lists, and he received the 1991 Emmy Award for a supporting role as a retired officer and grandfather in the ABC comedy “Davis Rules.”

His recording “Crank(y)cq Calls” won the 1995 Grammy Award for best spoken comedy album. Mr. Winters was the second-ever recipient of the Mark Twain Prize for American Humor, in 1999; Richard Pryor was the first.

Late in his career, Mr. Winters recorded voice-overs for animated films, including “The Smurfs” movies.

In a 1991 interview with the Los Angeles Times, Mr. Winters likened the entertainment industry to the Olympics, with actors standing on boxes to receive gold, silver and bronze medals.

“I think my place is inside the box, underneath the guy receiving the gold medal,” he said. “They’re playing the national anthem and I’m fondling a platinum medallion.”