John Mahoney as Martin Crane on Frasier. Photo: NBC/NBCU Photo Bank via Getty Images

John Mahoney was a Tony Award–winning actor, a longtime member of Chicago’s Steppenwolf Theatre Company, and a reliably great supporting player in numerous films. But when the news broke earlier today that Mahoney had died Sunday at the age of 77, practically every obituary and social-media post about him referred to him first as Frasier’s dad.

Mahoney’s role as Martin Crane, the salt-of-the-earth father of snobby psychiatrists Frasier and Niles on the NBC sitcom Frasier, unquestionably defined Mahoney’s career. It earned him two Emmy Award nominations and made him forever identifiable as the ex-cop who barked sarcastic remarks from his favorite La-Z-Boy recliner, the one with the stripes and the duct-tape patches on it.

When people describe that character, they tend to use words like “cantankerous” or “crusty,” which are not inaccurate. Martin Crane was emotionally closed off, sometimes grumpy, a man’s man, and a father who often had trouble understanding how his genes could possibly be linked to the ones inside his pretentious-sophisticate offspring, whom he loved even if he couldn’t bring himself to say it. But when I think about Martin Crane and what Mahoney brought to the part — what he brought to so many of the roles he played — I immediately think about the twinkle in his eye. It was that twinkle that allowed audiences to feel connected to him, to look past the flaws of the men he portrayed and connect with the joy, childlike mischief, and affection he felt for the people — or, in the case of Martin’s beloved dog, Eddie, the animals — in his characters’ lives.

In the first season of Frasier, in an episode called “Dinner at Eight,” the twinkle is on full display when Martin takes Niles and Frasier to a restaurant called the Timber Mill. Martin thinks the place is just great and can barely contain his glee when the hostesses, per tradition, cut off the neckties Niles and Frasier are wearing because they like to keep the atmosphere casual. “Dad, you could have mentioned that to us,” Niles (David Hyde Pierce) says indignantly. “And spoil the fun?” Martin says, with a big laugh.

Martin is really enjoying himself, which makes the moment when he becomes fed-up with his sons’ rude behavior — they can’t stand the place because it has (gasp!) a salad bar — that much more affecting. When Mahoney turned on that twinkle, he radiated warmth and good cheer; he was practically a Christmas carol in human form. But when he turned it off, the chill set in quickly.

He also flipped it on and off in two of his best film performances: as Jim Court, the seemingly upstanding father of Diane Court (Ione Skye) who turns out to be stealing money from nursing-home residents in Say Anything…, and as Perry, the diner who makes a pass at Olympia Dukakis in Moonstruck.

In a small but wonderfully relatable moment in Say Anything…, an elated Mahoney is driving and bursting with the news that his daughter has been accepted to study in England as part of a fellowship program. As people often do in Cameron Crowe movies, he expresses his elation by singing, in this case, Steely Dan’s “Rikki Don’t Lose That Number.” He can barely keep his mouth under control. It insists on smiling, and keeps on doing so in a subsequent scene when he flirts with a cashier while trying to buy luggage for Diane’s trip. When his credit cards are declined, the smile drops away like an elevator whose wires have snapped. He knows his time is up and the IRS is probably onto him. The light goes out in his eyes, and it’s painful because we remember how thrilling it was, just a few minutes earlier, when his electricity was still on.

In Moonstruck, Mahoney is less sad than pathetic as Perry, a professor who consistently dates (and gets dumped by) women who are far younger than he is. Dukakis’s Rose asks him why men chase women, and he explains, in a wonderfully natural monologue with his eyes cranked up to full twinkle, that he tends to fall for his students because he sees some idealized version of himself in their reverent gazes.

“It doesn’t last long,” he says of the relationships. “A few weeks, a couple of precious months. Then she catches on that I’m just this burned-out old gasbag, and she’s as fresh and bright and full of promise as moonlight in a martini.”

That’s what that twinkle in John Mahoney’s eye was. It was moonlight in a martini. It was unvarnished fatherly pride, which shined through for Diane Court, and often did, too, for Frasier and Niles. It was kindness and effervescence and life itself, and TV and film will be dimmer without its twinkle.