You know how there are things you didn’t particularly care for when you were a child – a corny AM radio song, a strange family dish – that, when you get older, become drenched in a sepia glow just because they belonged to the wallpaper of your youth?

That’s how I feel about the 70’s sitcom “Welcome Back Kotter,” about a high school teacher returning to his alma mater in Brooklyn to take over an unruly class of remedial students known as “The Sweathogs” (because their top floor classroom was always too hot).  The show launched John Travolta’s career.

I watched it when I was little – just ‘cause – but now, upon hearing that Ron Palillo, who played Arnold Horshack on the show, passed away, I feel a pang of sadness and melancholy.  Palillo died of a heart attack on Tuesday.

With a mere wave of the hand, Horshack could get a laugh.

The show was a bit broad for my taste, but you have to tip your hat to someone whose laugh became so iconic that to this day, people post stuff like “Baby Laughing Like Horshack.”

I couldn’t find a clip of him laughing on the show – legal issues, I’m guessing, but it was like a donkey braying – take my word.

Until stumbling across his obituary, I hadn’t heard Palillo’s name in decades.   And there is a reason for that.

His success.

“I know him, love what he does, not right for the part,” said Palillo in a 1997 interview, referring to what he said was the mantra of every casting director he met after his run on the hit show, which lasted from 1975 to 1979.  “Everybody thought of me as Arnold Horshack.  I resented Horshack for so many years.”

Palillo was on this earth for 63 years, yet his life – at least his professional life – became defined by those four years.  I looked him up on IMDB.  He has three pages of credits, but it’s nothing you’ve ever heard of – bit parts here and there – an appearance on “Trapper John, M.D.”, say, or “Cagney and Lacey.”

“I think producers could smell the desperation in me,” he once told a reporter.

His father died of lung cancer when he was ten, and he developed a stutter.  His mother thought getting him involved in local theater, in his home town of Cheshire, Connecticut, might help, and she was right.  He fell in love with the stage and overcame his speech impediment.

Instead he developed a goofy, hacking laugh for his Horshack character, and, while it propelled him to fame, it became another kind of impediment.  In the 1980’s, Palillo struggled with depression and rarely left his apartment.

But he seemed to find some peace of mind later in life.  In 2010, back in Connecticut, he directed the first production of “The Lost Boy,” a musical he wrote based on the life of Peter Pan author J.M. Barrie.  It struck me as completely unsurprising that he would choose to do a musical based on the life of a man whose most famous creation was a boy who never grew up: to the public, Palillo was frozen in time as remedial high school student Arnold Horshack.

Later in 2010, Palillo moved to Florida to be near his aging mother, and there he became a high school drama teacher.  I hope he was happy doing it.  His mother, mercifully, died last year, and so didn’t have to hear the news about one of her sons dying before her.

Palillo is survived by Joseph Gramm, his partner of 41 years.    I did the math.  They were together since 1971, when Palillo was 22.  Gramm saw his partner become famous as Horshack, then was there with him as he struggled through depression, and was still there with him when he found himself again.  And then, of course, when he slipped away.

That goofy laugh.  That goofy, goofy laugh.