The 1975 Academy Awards provided a stunning upset in the Best Actor category. Nominees Dustin Hoffman, Al Pacino, Jack Nicholson and Albert Finney, a veritable Mount Rushmore of acting legends, were beaten out by an actor who’d never had a major role in a movie before.

Art Carney, well-known to audiences as Ralph Kramden’s goofball neighbor Ed Norton in the 1950s sitcom “The Honeymooners,” had won over the Academy with his heartfelt portrayal of Harry, an elderly man who loses his apartment in New York and must find a new place to live for himself and his beloved cat Tonto.

Harry’s journey starts with a failed attempt to live with his son’s surly family in suburban New York. Searching for a new home, he and Tonto start a cross-country odyssey that leads to a series of adventures and delightful surprises. Hilarious and touching throughout, “Harry & Tonto” is one of Hollywood’s greatest road pictures, with the unusual twist of a cat serving as the hero’s sidekick.

One of the joys of the film is the series of vivid and quirky characters Harry meets on the road. There are notable performances by soon-to-be famous actors like Larry Hagman and Ellen Burstyn as Harry’s adult children. But director Paul Mazursky frequently cast non-actors who had the right look or quality for a role. He was rewarded with a series of unexpectedly realistic characters such as a cat salesman cowboy and a scene-stealing New York cabbie.

Shot on a shoestring budget, Mazursky frequently had to improvise locations and figure out how to shoot in tiny rooms with available light and little time to get it right. But the film was charmed by good fortune, unusually sunny weather, and a cat that seemed to have a knack for inspired improvisation. Mazursky was surprised a number of times when the cat deviated from the script, providing some of the film’s most memorable moments.

But the real story here is the remarkable performance by Art Carney. Subtle, nuanced, bold and surprising, Carney brings a life and reality to Harry that is a rare feat of acting. His relationship with Tonto is intimate and loving, and his wonder at the surprises the road has to offer is a joy to watch.

The film represented a personal and professional comeback for Carney. In the mid-1960s, while playing Felix in “The Odd Couple” on Broadway, Carney had a nervous breakdown in the wake of the collapse of his marriage. A longtime alcoholic and drug addict who suffered from severe depression, he spent six months in a sanitarium. Although this stabilized him emotionally and got him off drugs, the drinking continued. During the shooting of Harry and Tonto, the drinking brought on a health crisis that threatened to derail the film. Carney was finally able to quit, and finished the film, sober and clear-headed for the first time in years.

Carney’s performance in Harry and Tonto, coupled with his new found and lasting sobriety, brought about a career renaissance. He went on to star in a series of hit films such as “House Calls” and “Going in Style,” and public appreciation for his work and talent soared. And although he’ll be primarily remembered as Ralph Kramden’s sidekick, his performance in “Harry and Tonto” is perhaps his greatest achievement.