Sean Penn Smoking Colbert

Sean Penn blew into Late Night with Stephen Colbert, puffing on cigs like a steam engine. Cancer anyone? (Photo: CBS)

Sean Penn, the actor turned author, blew smoke–literally–on Late Night with Stephen Colbert last night. He smoked cigarettes during the interview, setting a fine example for young kids everywhere. Oh.. and he was high on Ambien (just a little) to boot.

But, hey, he had some encouraging words for the kids from Marjory Stoneman Douglas High School in Parkland, Fla., who organized the “March for Our Lives” protest in Washington D.C. and hundreds of other cities around the world.

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When asked if the kids “give him hope,” he replied:

“Within days of that not only are they stating their case with incredible sobriety and articulate words but in such an inclusionary way. You feel like there are reasonable people who have been on the other side of this conversation who will listen to these kids,”

Otherwise, Penn was looking worse for wear with disheveled hair and a cigarette hanging from his lip.

Colbert tried to talk a little sense into the Oscar winner.

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“Please don’t smoke anymore. I don’t mind. My parents smoked when I was a child so it gives me happy memories to smell cigarette smoke but you know we want you to be around for a long time and those things are bad for you.”

“Job security for oncologists,” Penn joked.

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Except that’s no joke. Cigarette smoking is one of the leading causes of cancer and lung diseases. Penn’s tough guy image kind of went out of style after chain-smoking actor John Wayne hacked up a cancerous lung back in the ’60s.

In any event, Penn was on the show to promote his new spy novel “Bob Honey Who Just Do Stuff: A NovelAdorable Lout Sean Penn Blows Smoke--Literally-- on Stephen Colbert (Watch!) 1.”

USAToday gives the book two and a half stars (out of four). It’s about a reclusive middle-age divorced man who’s traveled the world as a waste-management expert and sold fireworks to dictators.

He often freaks out his suburban California neighbors with his antisocial behavior and on the side is a secret agent who assassinates the elderly via a trusty mallet upside their heads.

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Sound familiar? We’re talking about Chuck Barris’s book “Confessions of a Dangerous Mind,” although Penn clearly drew some attributes of his character from himself.

The book will be available starting today (Mar. 27)

Check out the interview below.