Today, we are all Trekkies. But believe it or not, my fondest memory of Leonard Nimoy, Actor, involves Mr. Spock only inferentially. After Martin Landau bailed on the old "Mission: Impossible" series in 1969, Nimoy replaced him for a couple of dumpster seasons as a master of disguise known as “the Great Paris”—and ooh, was he roguish. He chortled and flashed his choppers as if each of his teeth had its own dressing room. His eyes were sparklers celebrating a year-round Fourth of July.

In other words, he was seizing every chance to remind viewers that He Was Not Spock, giving me my first inklings of what a cage a signature TV role can be. No wonder half the cast of "Downton Abbey" seems frantic to get killed off or sent to Boston—or, failing that, to at least get new attitudes and situations to play. Would you really blame Joanne Froggatt for breaking out the Champagne when Anna Bates’s rape gave her a reprieve from three seasons of selfless cooing? Emmy time!

In Nimoy’s case, we know how his great escape worked out. After a butterfly struggle against his fate—he was so balky about reprising the part that the script for 1979’s Star Trek: The Motion Picture originally omitted Spock outright—he played the character in count 'em eight features, guested as Spock on not only "Star Trek: The Next Generation" but on "The Big Bang Theory," and provided the voice for multiple video game versions. Except for, maybe, his fun role as a Me Decade shrink in Phil Kaufman’s 1978 Invasion of the Body Snatchers, whatever else he could do or might have done never came to much.

By comparison, William Shatner’s non-Trek career is a feast of variety. The difference between them is that Shatner’s ultimate contribution to pop culture is Shatner—Shatnerismus, Shatweltanschauung, he wouldn’t be Shatner if it could be defined—and Nimoy’s was Spock, a mantle he ended up accepting with grace. It did give him more dignity than Bill in the long run, even granting that A) that ain’t hard, and B) the Shat clearly had and has other priorities. Any sense of confinement Nimoy may have felt early on gave way to a healthy gratitude at his astounding good fortune. He was, by all accounts, a thoughtful man, and he must have realized that inadvertently helping to found a religion is no minor palliative to whatever thwarted ambitions he might have once nursed, to play somebody who smiled more and got laid a bit oftener.

Several thousand actors have played Hamlet more or less creditably before being forgotten. Even Sherlock Holmes—Spock’s most obvious egghead antecedent in Popland—is still up for grabs as new interpretations go. But Spock is even more impossible to imagine minus Nimoy than Nimoy is to imagine minus Spock, and Zachary Quinto—who has taken over the role in J.J. Abrams’s big-screen reboot—would probably be the first to tell you so. From where I sit, owning one of the dozen or so most emblematic, not to mention beloved, characters in TV history is an immortality that leaves Daniel Day-Lewis eating dust.

Because the character and the original series became so enshrined in the pop-culture pantheon, it's easy to forget that Spock was the most peculiar ingredient (those ears, that green blood, that dispassionate diction) on a mighty idiosyncratic show. Gene Roddenberry had an expert grasp of TV formulas and conventions, one reason "Star Trek" is such an anthology of tried-and-true genre moves under its sci-fi umbrella. His genius was for transposing them to unexpected contexts that let him express his distinctive idealism and humor. Captain Kirk’s half-Vulcan science officer was at once a classic sidekick and a mold-breaking variation on the same. Keeping those two attractions in balance was the essence of the part.

Plenty has been written about the Spock/Kirk relationship’s uncanny American pedigree as we’ve replaced one final frontier after another: Jim/Huck, Queequeg/Ishmael, Chingachgook/Natty Bumppo, not to mention Mr. Peabody and Sherman. Yet Star Trek was firmly rooted in cultural changes specific to the ‘60s, and that’s why we were also watching a pan-galactic parable of the ultimate goy (moronic but zesty) and the ultimate Jew (brainy and long-suffering) thriving on each other’s presence in an era when Jewishness was making the leap from exotica and/or ostracism to mainstream chic. Whether or not Roddenberry planned that subtext, Nimoy, Jewish himself, was certainly aware of it. As most Trekkies know, the Vulcan “Live long and prosper” salute, which Nimoy devised, derives from a blessing representing the Hebrew letter standing for “Almighty,” as in God. In any history of American Judaism’s greatest crossover decade, Spock deserves a place alongside Bob Dylan, Philip Roth, and Barbra Streisand—and, I guess, Henry Kissinger, too.

Like they say, pop culture sure does move in mysterious ways. Though Nimoy had genuine skills as an actor, they weren’t on a par with, say, Alan Rickman’s. Yet Rickman was the one who ended up paying tribute to Nimoy’s legend in Galaxy Quest. Who’s to say which man might have envied the other’s stature more? Whatever Rickman’s past and future accomplishments, he’ll never get to be part of TV’s version of the Beatles—who, unlike the originals, reunited, and reunited, and reunited until the cows came home. By Grabthar’s hammer, I can think of many worse lives.