We're told occasionally that what goes around comes around to such a degree that going around again and coming around could be called great American indoor sports. In this corner, the unofficial world heavyweight champion: Leslie Nielsen, who was merely a pretty good actor through most of his career and then, in its final couple of decades, became a sprite, a spirit, a tremendously engaging ridiculous presence in such films as "Airplane!" and "The Naked Gun."

It was a jolt to learn, as we did Monday, that the Canadian-born Nielsen had attained the age of 84 when he died Sunday in Los Angeles. He not only looked younger, and acted younger, but also seemed to think and dream and be younger. He was young at heart and young in the head, and both of those, in this context, are really just gentle ways of saying he was "nutty as a fruitcake" and as infectious as the measles.

What endeared him most to movie audiences was the fact that he appeared to be having a heck of a good time while doing his best to see that the audience had one, too. His performances were masterful, instinctual satires of modern behavior, and he became the quintessential clueless dork, someone who got it all wrong, whatever "it" was, and never stopped to apologize for his mistakes - usually because he didn't even recognize them as such.

Nielsen's nuttiness was a gift, but it wasn't until fairly late in life that he got to ply it as a trade. In the '50s and most of the '60s, he was vanilla pudding and cast as such - characters on the verge of being dull and dopey. He couldn't really throw heart and soul into these parts because the characters lacked hearts and souls themselves. He could just do his best to hang onto his dignity.
The epitome of sorts was reached in 1957 with "Tammy and the Bachelor," in which Nielsen played the good-looking "older man" on whom perky, quirky Tammy (tolerably adorable Debbie Reynolds) shamelessly doted. Nielsen had no easy time trying to conceal his disdain for the movie, especially because he'd had brush with greatness one year earlier by starring, with Anne Francis and Walter Pidgeon, in "Forbidden Planet," a lavish sci-fi picture from MGM that had its roots in Shakespeare, no less.

As J.J. Adams, commander of an interplanetary cruiser bopping around space in the very distant future, Nielsen gets to romance Francis as Altaira, presumably virginal daughter of Dr. Mobius, who's been running the planet, so to speak, ever since the crew members he arrived with years earlier were all hideously murdered in their beds by a big invisible monster. It sounds a lot sillier than it plays; "Planet" is actually one of the best-looking, more thoughtful of the decade's space-travel pictures.

Still, it's conceivable that Nielsen got the giggles while filming scenes in which he fired his tiny little "blaster" at the big monster, the blaster's destructive ray matted in later by the special effects department. As usual in films like this, Nielsen had to point at objects that weren't really there and shudder in fear at a creature that took its own sweet time about becoming visible.

Nielsen was a reliable pro by this point, having learned his craft, and mastered the fine art of ad libbing when things went wrong, on television. Yes, that. In the '50s, much of prime-time television originated in New York, and theater folk picked up extra bucks by appearing in the ambitious anthology shows that the three major networks all aired regularly (Fox didn't exist at this point). In a 1991 interview in Washington, Nielsen estimated he'd made 1,000 TV appearances when he and the medium were young.

He'd also appeared in 50 movies, he said - yet was almost creepily under-noticed, nearly as invisible as the big, bad monster that ransacked "Forbidden Planet." Perhaps he blended in too well with the furniture. Or maybe he was always-good, never-great, as many a journeyman actor tends to be.

But television, where Nielsen had put in hours and hours of hard labor, would be his deliverer as well - in the 1980s, when the mad and wacky Zucker Brothers cast him in "Police Squad!," a hilarious parody of the old Quinn Martin crime shows that networks loved to buy for their schedules. Each episode of "Police Squad" opened with the evening's guest star being killed, usually in the proverbial hail of gunfire; Robert Goulet, Florence Henderson and several others fell into gutters and died in the opening moments of the program.

Nielsen was the new Deadpan Prince with his portrayal of Lt. Frank Drebin, chief of Police Squad, a "special unit" of the force that seemed utterly unshackled by such niceties as the civil rights of suspects. Nielsen started a new life as a very sly and wily comic actor, a perfect combination of actor and role. Unfortunately, the humor was too quick and smart for the executives at ABC, who canceled the series after its initial order of six episodes had aired.

In 1988, "Police Squad's" files would be reopened for a series of near-riotous motion pictures, starting with "The Naked Gun: From the Files of Police Squad." Nielsen's unassuming, understated performance as Drebin worked just as well on the big screen as it had on the small one. The Zucker boys thought of advertising the first movie as coming "from the failed TV series!" - but feared the audience might take that too seriously and stay away.

Nielsen's breakout, breakthrough comic role had come eight years earlier, again courtesy of the Zuckers and their partners in comedy, with "Airplane!," a joke-a-minute spoof of films about travelers in distress; the old "Bridge of San Luis Rey" gambit turned into splendid and sensational farce. From that point on, Nielsen romped and bopped from one spoofy farce to another, always "playing it straight" and yet with a gleam in his eye that seemed a tiny but important bit of actor's inspiration.

Discussing the first two "Naked Gun" films in 1991, and admitting, to the Zuckers' consternation, that the first was better than the second, Nielsen talked about maintaining dignity even in absurd and surreal surroundings. Nielsen concluded the brief dissertation thus: "Then again, if it's funny, then the hell with dignity."

Nielsen was traveling in the company of a whoopee cushion on that press tour and even brought it onto "The Tonight Show" and other such programs, as if he were an obnoxious guest at an otherwise proper cocktail party. In the best traditions of American comedy, from its beginnings through the crash-bang comedies of the 1990s and 2000s, Leslie Nielsen skewered the otherwise proper, did it with mischievous delight and convulsed audiences mercilessly.

He had a good time giving a good time. Life may not get better than that.