Once you’ve gone viral, there’s no turning back.

That’s the hard lesson for a Seattle cartoonist who sketched some doodles and unwittingly launched a movement.

Molly Norris, a reluctant phenomenon, wants to return to her quiet artist’s life, the one she lived largely unnoticed until she drew the Prophet Muhammad — as a spool of thread, a box of pasta, a cup of coffee, a domino, a cherry and a doggie purse.

Take your pick. Since depictions of Muhammad aren’t allowed under some (but not all) interpretations of Islam, no one knows what he looks like. And, bummer alert, anyone who tries to capture his likeness is subject to punishment by death.

The text on Norris’ cartoon, a poster calling for a national “Everybody Draw Muhammed Day” on May 20, reads: “Will the REAL likeness of the prophet Mohammed please stand up?!”

Clever girl, but perhaps too clever?

Her idea, which Norris insists was intended only to serve as a stand-alone cartoon — not a movement! — has spawned a Facebook page that boasted almost 8,500 members by Tuesday morning. Apparently, lots and lots of people want to see this thing through.

Not Norris, who was merely trying to express solidarity with Trey Parker and Matt Stone, the “South Park” creators threatened by a radical Muslim group (or 12 guys and a website) offended by a recent episode not depicting Muhammad. Actually, the cartoon Muhammad was wearing a bear costume.

Horrors. (One can’t even muster the requisite outrage to install extra exclamation points.) But seriously?

Seriously!

One Abu Talhah Al-Amrikee (aka Zachary Chesser of Virginia) posted a warning on the Revolution Muslim website suggesting that Parker and Stone might wind up the way murdered filmmaker Theo van Gogh did. Van Gogh’s offense was making a film about Islam’s abuse of women.

In response to the threat, the bosses at Comedy Central knelt before the altar of — no joke — political correctness and censored a subsequent episode, bleeping all mentions of Muhammad, as well as a short segment about fear and censorship.

Who could have guessed that the clash of civilizations would be fought by cartoon characters?

Enter Norris, who had the simple idea that this was silliness and deserved further poking. And then things really got out of control. Norris wants out and has begun to distance herself from the fray, which has taken on a life of its own.

Until recently, her website featured a banner: “I am NOT involved in ‘Everybody Draw Muhammd (sic) Day!’” A new cartoon shows Norris wearing a peace-sign T-shirt seated at her drawing board in a swirl of balloon thoughts: “I am a cartoonist. I never elaunched’ a day to draw Mohammed.” “Good thing I am married to a SUMO WRESTLER!” “This was always about the freedom to draw what we want in the U.S.A.” And perhaps most to the point:

“I have hit some kind of gigantic nerve.”

Indeed you have, Ms. Molly. But there’s a reason you hit a nerve, and it bears further discussion. Gigantic nerves are repositories of truth. Once you’ve tapped one, exploding electric currents ricochet across the landscape of the human psyche. A light goes on in a Seattle studio, and suddenly the nation is illuminated by a bright idea.

The truth is that Americans love their free speech and have had enough of those who think they can dictate the limits of that fundamental right. Americans also love humor and the irreverence that underpins the joke.

You might say irreverence is our national religion. It keeps us from taking ourselves too seriously and from killing each other over differences of opinion. Cartoons get under our skin in special ways, driving past our defenses and aiming right for the heart of our self-importance. That’s why we respond so emotionally.

Barring the occasional offensive punch line, humor is a mostly pleasant test of our allegiance to founding principles. Think of it this way: The degree to which one can tolerate ribbing about one’s most deeply held convictions is the degree to which a society can remain free. We honor that notion through our laws and our sense of humor. We may not all laugh at the same things, but most understand that it ain’t personal.

Norris’ cartoon was a fine idea, but she should be relieved of further duty or responsibility. As for the rest of you characters: Draw to any heart’s discontent. It’s a free country.

For now.

Kathleen Parker writes for the Washington Post. Her e-mail address is kathleenparker@washpost.com.