If it walks like a duck and quacks like a duck, it might have just been fired for tweeting about the Japanese disaster.

The news that Gilbert Gottfried has been fired as Aflac spokesduck after making inappropriate jokes about the Japanese disaster on Twitter provoked a single response:

Wait, Gilbert Gottfried was the Aflac spokesduck?

This raises two questions:

First: Is this off-limits?

Everyone’s been calling these “inappropriate jokes.”

Is there any other kind?

The jokes are terrible – as Gottfried quipped, “in Japan, they’re all sinking.”

But comedy is supposed to dwell at the edge. Freud once described jokes as the conscious expression of thoughts usually barred by society. The stuff of comedy is the subjects you otherwise might not be able to broach. It’s laughter that serves to break the ice of convention and taboo.

After all, appropriate remarks can only be so funny. This is why most after-dinner speeches completely vanish from memory, while an improper barb from W. C. Fields – “I like children – fried” – can linger in the memory far longer. (I had a more inappropriate quote, but this is a family Web site.)

Humor exists to break taboo. But are there some that should never be broken?

In prior decades, there were all kinds of taboos. Visible ankles? Taboo! Opt out of an arranged marriage? Mega-taboo! Skip a drawing-and-quartering to go practice religious tolerance? Never show your face here again!

But now, like the polar ice caps and much of Joan Rivers’s face, the taboos have melted away. Remember George Carlin’s words you couldn’t say on television? That was a scant 40 years ago, and now we have a TV show called “$#*! My Dad Says.”

The list has dwindled. Sex? Hardly taboo, these days. But rape? Still taboo. Death? Still taboo. Talking about a tragedy right after the fact? Definitely taboo. Even years after the fact – I once joked in a column about the Hindenburg, and several people sent me irate telegrams – some situations, in many minds, will never permit levity.

Sure, it has shock value. But what’s the point in opening this particular can of discourse?

Tragedies bring out the best in people. But they also bring out the seamier side, and with the Internet, that’s easier to spot than ever before. It used to be, you had to be Glenn Beck to get people riled up by calling such a disaster God’s work. Now any fool with a camcorder can do it.

And look at all the people whose Facebook statuses are suggesting this is payback for Pearl Harbor, of all the fundamentally absurd and terrible things to suggest.

I’ve written before about the people who use the hush that follows any tragedy as an opportunity to make their voices heard.

But there’s a difference between shouting and comedy. In comedy, Too-Soonerism is a delicate art. These jokes are the jokes everyone knows will produce a visceral reaction, touching the one subject that is absolutely off-limits.

But so little is off-limits anymore that comedy might be on the brink of an existential crisis. Have all the idols worth smashing been smashed? Will we ever stop? Or do we keep right on smashing?

Still, as long as there have been tragedies, there have been people who made jokes too soon about those tragedies. There’s a very tasteless reference in Aristophanes’s Clouds to some skinny, pale philosophy students who look “like the prisoners from Pylos.” And that was 423 B.C.!

After Julius Caesar was stabbed, I’m sure the Gilbertus Gottfrieduses of his time started making quips like, “I hear Caesar’s doctor told him to try acupuncture! Too much enthusiasm, Julius!” “Hear Caesar address the forum? I’d rather be stabbed to death!” “Waiter, I thought I ordered a Caesar salad, but this one is chopped!”

Communal tragedies provoke an emotional reaction. And they can be a source of kinship with an audience that increasingly hasn’t read the same books, seen the same movies, or learned the same historical facts — except for the big shocking ones. Sure, for Johnny Carson, it was still too soon to joke about the Lincoln assassination, but Sarah Silverman can quip edgily about Sept. 11 and people get it. By saying something knowingly inappropriate, you can draw out some of the bile. The laughter is coupled with shock — or should be.

Gottfried’s lost his voice gig and attracted his share of opprobrium. But he’s also receiving an unsurprising amount of support.

I’m not saying Gottfried’s jokes were hilarious. But maybe we should consider the impulse behind them.

Impropriety has long been Gottfried’s comedic stock in trade. Post-9/11, he made an inopportune joke at the Friar’s club roast about his flight’s having to stop off at the Empire State Building. That time, he was able to drag himself out of the hole by telling The Aristocrats. Now, he might not be so lucky.

The second question? Who listens to a duck?