"We have all lost a gracious human being who will always be remembered for his portrayals of the human condition," Phil Brock of the Studio Talent Group said in a statement. "Pat had the ability to bring laughter and kindness to any role. The twinkle in his Irish eyes let you know that you were in on the joke. His was an extraordinarily impactful long lasting career."
He died Wednesday, according to a Facebook post from his daughter Tresa Harrington.
"Dear Friends, it is with the most unimaginable pain and sadness, that I tell you my father, Pat Harrington, Jr. passed away at 11:09 PM this evening," she wrote, accompanied by a picture of her father as Schneider. "We were all with him today and tonight: crying, laughing and loving him. This is the single most heart wrenching and physically painful thing, I've ever had to endure."
She added, "My heart is broken to pieces and I will cry and cry until I just won't. Love to you all! And as we head into this year, never be afraid to tell the people you love, that you love them."
Harrington hit it big as a comedian in the 1950s, part of "Tonight Show" host Steve Allen's group of "Men on the Street" (which also included Tom Poston and Don Knotts).
Always a regular presence on TV and in movies, in the '60s and '70s he appeared on a number of series as a guest star or semi-regular, voiced the Clouseau-like Inspector in the cartoon spinoff of "The Pink Panther" and had a small role as an emcee in the 1972 Robert Redford movie "The Candidate."
But it wasn't until "One Day at a Time," in which his wisecracking super always seemed to be at hand for Bonnie Franklin's single mother, Ann Romano, and her two teenage daughters, that Harrington broke out to widespread success.
The show, which was produced by Norman Lear during the peak of his 1970s TV dominance, ran for nine seasons, from 1975 to 1984. Harrington was there for all of them.
In a reunion special
, Harrington explained the attraction of the character.
"You had a middle-aged, single man who was lonesome. Look what landed in his lap: a ready-made family! A gorgeous woman I figured I could hit on and two kids who needed to be straightened out," he said in the special. "And then it became the story of a divorced woman with two young teenage girls being raised by a handyman."
Schneider fancied himself a Casanova and always made a big entrance into the Romanos' Indianapolis apartment, forever clad in jeans, T-shirt and vest, a Clark Gable mustache upon his lips, a cigarette pack rolled in his sleeve. The entrances were inspired, he said in the special, by Art Carney's antics on "The Honeymooners."
He also got some of the best lines. Asked in one episode whether he thinks he's hot stuff, Schneider replies, "Let me put it this way. The ladies in this building don't call me 'super' for nothing."
"I was a blank slate, and he taught me how to be funny," she said.
"They were easy to be with," said Harrington. "They were so bright."
Bertinelli posted a photo of herself with Harrington on Instagram Thursday.
"He always made me laugh," she wrote.
Harrington stayed busy after "One Day" went off the air, continuing to guest on TV shows, to voice cartoon characters and to wink at the Schneider character on episodes of "The King of Queens" and "Hot in Cleveland" (the latter with Bertinelli).
The cast made occasional reunions over the years. Franklin died in 2013
Harrington was born Daniel Patrick Harrington Jr. in 1929 into a showbiz family. His father was a vaudeville performer whose own career had its ups and downs. Harrington, who went into show business after college and military service in the early '50s, had much better luck.
But even he couldn't outdo Schneider for fame. The character was so distinctive, Harrington could go unrecognized in a crowd, he told the Los Angeles Daily News in 2008
"Without the mustache and the attitude, they're not gonna get me," he said.
According to the Internet Movie Database, Harrington is survived by four children.