Most nights, from the witching hours of 2 to 4am, Steve Martin finds himself awake, his thoughts spinning.
He lies in bed and imagines absurd scenarios: a family of cows sitting down to a fancy dinner; a duck carrying a rifle; a washed-up Tarzan pitching reverse mortgages on television.
He jots the ideas down on his iPhone and turns the best ones into cartoons.
Martin - a comedian, actor, writer, producer and Grammy Award-winning bluegrass banjo player - is one of the entertainment world's most overachieving multihyphenates.
He has written essays, a memoir, novels, plays, screenplays, stand-up monologues, songs, sketch comedy and short fiction. But cartoons, which he calls "comedy's last frontier", were among the few comic mediums that eluded him, in part because he lacks an essential skill.
"I can't draw," he said. "I'm one of the few artists where the paper becomes less valuable when I draw on it."
As an aspiring cartoonist with no artistic ability, Martin was in a tough spot. So last year, he contacted illustrator and cartoonist Harry Bliss and asked if he wanted to work together.
Bliss was interested. Over the next six months, they created around 200 cartoons, many of which appear in their new collection, A Wealth Of Pigeons, which Celadon Books will release today.
The comics vary in style and tone, from absurd, silly and whimsical cartoons featuring talking animals and bored aliens, to more meta, philosophical ones about the creative process and the elusive, subjective nature of comedy.
One cartoon shows an astronaut planting a flag on Mars, thinking: "I just hope this doesn't define me."
Another shows a scowling woman with her suitcases heading out the front door as a swamp monster looks at her sadly and asks: "Is it the slime?"
In another, two moles stare at a mountain in the distance, and one says: "It started out as a molehill, but then I just kept going."
The medium's constraints appealed to Martin. "What I like about them is they're so tight and they're so clean," he said. "It works or it doesn't."
During a joint video interview, Martin and Bliss described their collaboration and how they build on each other's ideas.
"The feeling of success is really interesting when you just land on it," Martin said. "It's almost like, I don't know how to describe it, it's a little pop and you go, 'Oh, yeah, that's an idea.'"
"It's a eureka moment," Bliss suggested.
"Yeah, I guess so," Martin said, sounding sceptical. "Except it's less than that. They found gold."
Sometimes, Martin sends Bliss a description of an image, with a caption he has in mind, and they workshop it a bit over e-mail.
"Art museum, mother and child looking at a painting. Mother: 'My kid could do that.' The kid is a tiny little Picasso wearing a smock and holding a palette," Martin wrote to Bliss this year.
"Lots of variables here. They could be looking at a Rembrandt and the kid is a tiny Rembrandt, or looking at an abstract and the kid is a tiny Pollock."
Other times, Bliss sent Martin an image in need of a caption. In one, a dog hides behind a tree, speaking into a walkie-talkie and hatching a plot to kidnap a squirrel.
Martin sent Bliss some options, including "This is badger, come in, centipede", "This is cowboy, come in, sidewinder" and "This is Roulette, come in, Yahtzee". Eventually, they landed on a variation: "This is Blackjack, come in, Yahtzee."
Occasionally, when Bliss could not visualise exactly what Martin has in mind, he has asked him for a rough sketch.
When Martin had an idea for a cartoon that debunks the myth of Sisyphus, Bliss could not quite picture it, so Martin sent him some stick figures, with lines like "Real Name Manny".
As collaborators, Martin and Bliss have a sort of odd-couple dynamic. "He's a country boy and I'm a city boy," Martin said.
Bliss, 56, who publishes his cartoons and illustrations in The New Yorker and in a syndicated single-panel comic that runs in newspapers, is a nature lover who lives in Cornish, New Hampshire (in J.D. Salinger's former home).
Martin, 75, is best known for his comic turns in films like The Jerk (1979) and Father Of The Bride (1991), and for his stand-up and sketch comedy.
He has made a career detour towards writing books, with his memoir, Born Standing Up, his novella Shopgirl and his novels An Object Of Beauty and The Pleasure Of My Company.
"You can see how respectful the collaboration is. It's not Harry drawing Steve's ideas or Steve captioning Harry's cartoons," says Ms Francoise Mouly, art editor of The New Yorker, who helped connect Martin with Bliss. "It's two guys trying to make each other laugh."
For Bliss, who normally works alone, collaborating with Martin was a daunting prospect at first. But Martin put him at ease by assuring him that he would defer to the comedic logic of the medium.
"One of the things early on that Steve e-mailed me was that he has no ego about capitulating to serve the cartoon," Bliss said in a follow-up telephone interview.
"To say 'No, this doesn't work' to Steve Martin is a hard thing to wrap my brain around. It's not that it's not funny in most cases, it's that his idea doesn't translate to the form."
A Wealth Of Pigeons includes some self-referential comic strips that show Bliss and Martin at work.
In one, they fight over whether or not a cartoon is funny, with Bliss telling Martin, "You're no Charlie Chaplin" and Martin countering, "And you're no Rembrandt."