In his new film, the British comedy I Give It A Year, he plays a best man so lacking in social graces he makes David Brent look like Richard Gere.
It was courtship of a kind that led to him taking the part. "It was like being hounded for a date," he says of writer-director Dan Mazer's entreaties, "and I finally agreed."
Then there was the time, before setting off on a stand-up tour called Hello Ladies, that he joked about it being a ploy to meet someone.
"Some women did take that a little too seriously. There were letters and they'd send photographs and what I can only describe as love resumes – 'I was in a relationship for two years, that ended in 2001, and now I live with 18 cats.' I started to find it a little bit eerie and a bit odd so I had to step back from the idea."
Having said all that, Merchant does get to go on a date with Halle Berry in the recently released Movie 43, although the liaison includes an unfortunate tattoo, a male striptease and extreme plastic surgery.
Merchant, 38, had an easier time of it on I Give It a Year, the story of a couple, played by Rafe Spall and Rose Byrne, who meet and marry quickly. As best man, Merchant gives a spectacularly gauche wedding speech. How gauche? Mazer was the writer of the Sacha Baron Cohen comedies Borat and Bruno: it's that squirm-inducing. Facing Merchant on the day was a marquee full of determinedly stoney-faced people. "One of the things about being an extra is you've got to not ruin a scene, so you do this long comic monologue and 200 extras would stare at you and you'd think, 'Oh God, I'm really dying on my **** here." Once "cut" was called, though, they laughed. It's quite an unsettling experience."
Merchant, 39, knows a bit about extras, of course. After the success of The Office, bit-part actors were the next subject of Merchant and his writing partner Ricky Gervais. The two later wrote and directed a film, the warmly received Cemetery Junction, set in the 1970s.
I Give it a Year certainly defies the notion that British film comedies have left the more daring material to the Americans. Merchant, who grew up studying how comedy was put together like other kids made Airfix models, thinks there has always been a note of edginess in British comedy, going back to Ealing and continuing with Monty Python.
He sees Mazer's movie as more in the tradition of "awkward social comedy" as seen in Fawlty Towers, Alan Partridge and The Office. Though it takes on the Americans, there's a particularly British balance to the film, he reckons. "He manages to keep a sweetness to the film, I don't think it ever gets kind of mean spirited or gross out."
Mention of gross out brings us to the ensemble comedy Movie 43. "So revolting it makes American Pie look like Casablanca," was the verdict of one critic. Another called it "the worst film ever".
Merchant says there was nothing in his scene with Berry at which he baulked. "I'm fairly uninhibited as a performer. I'll go gung-ho if you want me to do a bad striptease or wear comical prosthetics. I'm much more awkward and anxious in real life than I am when I'm performing."
With previous parts in Tooth Fairy and Hall Pass, Merchant, like Gervais, is establishing a foothold in America. Acting supplies a break from the pressures of writing and directing.
"Normally they ask me to basically be a sort of awkward British nerd, which is not really a stretch for me. So it's always really enjoyable. Someone picks me up in a car, takes me there and my job is to just try to be as amusing as I can and go home again. It's like a day off from my real life."
He's currently working on an HBO special with Gervais of Life's Too Short, their comedy about an actor and talent agency boss who is a dwarf. He is writing a new show, also for HBO, based on his stand-up, Hello Ladies.
Though known as a comedy writer and performer, he would like to write more serious material. This is a man, after all, whose favourite film is The Apartment, Billy Wilder's tale of sweetness and slight tragedy. "Just a very human film."
He is increasingly drawn to writing drama. "That's the stuff I watch. I don't tend to watch comedy, it's not really my thing, weirdly, any more. I guess I'm soaked in it."
But one step at a time, he says. "A lot of people still don't even know me as a performer so it's worth making people aware of my comedy turn then think about dramatic stuff later."
Born in Bristol, Merchant's dad was in insurance and his mum was a nursery nurse. At the University of Warwick he studied film and literature and worked in the radio station. From there he did stand-up, moved to London and was hired by Gervais to do a radio show. The Office came along in 2001.
Like Galton and Simpson, Clement and La Frenais before them, Gervais and Merchant's success had a lot to do with their boldness. Their willingness to have characters do or say the previously unsayable delighted audiences tired of My Family-style blandness.
That same daring, however, might now be working against Gervais. Derek, his television comedy about a man with learning difficulties, began a new series this week, despite mixed reviews for the last one. Life's Too Short ran for one series on the BBC before being picked up by HBO.
It wasn't that it failed to be recommissioned, says Merchant; he and Gervais just did not want to do another full series. Didn't it hurt, I ask, that it wasn't well received? "I can't feel like I make creative decisions or career decisions based on that."
This "go your own way" attitude was in evidence when Merchant, then a student, got together with friends and took a sketch show to the Edinburgh Fringe. They played to just six or seven people, he recalls, but had a blast.
"That was invaluable for me, it was one of the things that helped me to feel maybe I could try to do this for a living."
And he has. There are no plans to move to America permanently. Too many family and friends here. He does find the States "seductive" though. "There is a kind of get up and go optimism about the place that's exciting." He likes the American way of writing too, with its competitive, team-like style. On Hello Ladies he is one of a team of three.
In case you are wondering, Merchant, true to his character in I Give it a Year and Hello Ladies, remains single. He did not, probably wisely, respond to those who got in touch after his pre-tour plea.
"I felt like engaging in a dialogue might just be a little bit weird."
I Give It a Year opens on February 8.
