Jonathan Winters, who has died aged 87, was a moon-faced American comedian with a remarkable gift for mimicry which he deployed in manic improvisations featuring a cast of misfit characters that ranged from delinquent old ladies to country bumpkins.

Jonathan Winters in It's A Mad, Mad, Mad, Mad World 

He came to notice in Britain when he played the slow-witted removal lorry driver in It’s A Mad, Mad, Mad, Mad World (1963), an ensemble film with an all-star cast, mainly comedians and comic actors chosen for their verbal skills.

Once defined as “more intense than Bob Hope, more restless than George Burns or Jack Benny, more fleeting than Lenny Bruce or Richard Pryor”, Winters was an energetic pioneer of impromptu standup comedy in the 1950s with an outlandish line in free-form monologues.

But while he was raising laughs with his unscripted verbal flights of fancy, facial contortions and self-generated sound effects like dripping taps and rushing waterfalls, the pressure of touring led to a mental breakdown, and he was diagnosed with bipolar disorder.

Rejecting the conventional stand-up comedian’s reliance on quick-fire jokes, Winters entertained in a stream-of-consciousness style that could stray into the surreal. As well as his remarkable ear for voices and characters, he could transform the most mundane object into an instrument of mirth. On one American television show, Winters was handed a foot-long stick and became in turn a fisherman, violinist, lion tamer, canoeist, bullfighter, flautist, delusional psychiatric patient, British headmaster and Bing Crosby’s golf club. “Improvisation is about taking chances,” he would say, “and I was ready to take chances.”

Jonathan Harshman Winters was born on November 11 1925 in Dayton, Ohio. An only child in a prosperous family, whose parents divorced when he was seven, he spent much time entertaining himself. He described his father as an alcoholic, and regarded his paternal grandfather — an eccentric extrovert as well as proprietor of the local bank — as his principal influence.

At 17 Jonathan left Dayton High School, joined the Marines and served two years in the South Pacific during the Second World War. On his return he attended the Dayton Art Institute, where he developed his keen observational skills, and met and married a fellow student, Eileen Schauder.

At her suggestion, he entered a talent contest and won first prize (a wristwatch) by doing impressions of film stars. This led to a job presenting the early morning show on a Dayton radio station in which he would create characters and interview them using two voices.

Winters moved to New York where he soon made a reputation in stand-up comedy clubs. One night after a show, an old man sweeping up suggested that instead of mimicking the rich and famous, he should draw on people he knew. Within a couple of days, Winters had devised one of his most famous characters: a hard-drinking, dirty old woman called Maude Frickert, modelled in part on his own mother and an aunt.

High-profile appearances on television specials and chat shows followed and Winters soon built a following. But his career faltered in 1959 when he succumbed to depression and drink, and he burst into tears on stage at a nightclub in San Francisco. Taken into custody by police who found him climbing the rigging of an old sailing ship, and claiming he was from outer space, Winters spent eight months in a psychiatric hospital.

A turning point in his recovery was his role as the browbeaten furniture removal man Lennie Pike in the slapstick film caper It’s A Mad, Mad, Mad, Mad World. “I was fresh out of the hospital. I didn’t know if I was up to doing a picture such as this,” he recalled. But he took the part at his wife’s insistence, and “I finally opened up, I realised I was back, and I was in charge of myself and my mind”.

Roles in other films followed — he played two brothers in the film adaptation of Evelyn Waugh’s The Loved One in 1964 — as did further television shows, including his own. In 1981 Winters was cast in the sitcom Mork and Mindy, teamed with Robin Williams, an admirer whose own gift for off-the-wall improvisation made him the Jonathan Winters of his generation.

In later years, Winters contributed to numerous cartoons and animated films, playing three characters in the film The Adventures of Rocky and Bullwinkle in 2000. His recent work included voicing Papa Smurf in the 2011 live action film The Smurfs, and a sequel due to be released in July.

Winters won two Grammys, and an Emmy for best supporting actor as Randy Quaid’s father in the American sitcom Davis Rules (1991). He was awarded the Kennedy Centre’s second Mark Twain Prize for Humour in 1999, a year after Richard Pryor.

As a trained artist, he often introduced humour into his pictures and sketches. Among his books was a collection of short stories called Winters’ Tales (1987).

Jonathan Winters’ wife, Eileen, died in 2009. Their two children survive him.

Jonathan Winters, born November 11 1925, died April 11 2013