Stephen Colbert had Sean Penn on Late Show to discuss his new book, “Bob Honey Just Do Stuff,” which Colbert described as a novel about a septic tank salesman turned assassin who kills old people with a wooden mallet and thinks the country might be in need of his services to get rid of its fictional POTUS.

“Have the Secret Service contacted you? Colbert asked. “That’s the sort of thing you can’t even make jokes about. That’s the sort of thing they take very seriously.”

“This is a fiction, about fictional people,” Penn said of his book, out today.  “It is, on other hand, also a kind of venting,” he acknowledged to Colbert. During which, Penn smoked a cigarette, one of two he smoked during the two segment interview.

And when Colbert kicked off the interview [watch Part 2 below]  noting Penn seemed very low key, Penn told him, “You’ve inherited little of the Ambien had to take to get to sleep after a red-eye last night.”

“Sean Penn Smoking & On Ambien” People magazine screeched in its headline – among the many media outlets that went all Ladies Of River City about Penn’s appearance on the CBS late-night show.

Penn spoke passionately about last weekend’s massive, student-inspired march demanding Congress move on gun control measures, the importance of the 2016 election, and more.

“What happens as you get older is your idealism gets chipped at a bit. You’re looking for hope and, in my case, to get to 57 years old and when I need hope the most it’s harder and harder to find,” Penn told Colbert. Writing the book, he said, was his way to have “a kind of operating-room laughter and not just spend my time angry.”

Then Penn warned viewers, “whatever is going on right now has a lot more to do with an electorate that did not get mobilized than the result of that.”

“Sean Penn’s Smoking Colbert Interview,” CNN squealed, gushing that it was Penn’s puffing that “garnered a great deal of attention from viewers.”

After he finished writing the book, “this horrible shooting happens in Parkland and all of a sudden you have these kids who have gone under combat level horror…seeing friends maimed and killed,” Penn said.

“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 are going to listen to these kids,” Penn added, optimistically.

If the student-sparked movement does wind up affecting the ballot box in midterm elections, Penn said, “then I might write a less dystopian book.”

“Sean Penn admits he’s on Ambien, smokes on air in bizarre Colbert interview,” Fox News scolded.

Colbert reminded viewers the well-respected actor has said he’s tired of that pursuit.

“It’s always been the case for me that it’s all  about where you engage in expression creatively,” Penn explained. “And, as I got older – the greatest thing that an actor can bring to the party is to play well with others; it’s the collaboration. And I increasingly don’t play well with others.”

“I got to the point where I just felt…even people involved in creative process had become so self-censoring,” he said of Hollywood.

“I think part of it is that the girl I fell in love with was going into a movie theater in the dark with strangers and seeing something that might last forever. And now there is so much content, I can’t keep track of it and nothing seems special.”

“Sean Penn Smokes Cigarettes And Says He’s Sick Of Acting During Bizarre ‘Late Show’ Appearance,” Washington Post hollered.

Watch Part 2 of the interview here: