When I go to meet Paul Rudd at a low-key restaurant in Tribeca, I am early. A busboy is dragging a marble-topped table out the door while arguing with a tall and elegant woman. I circle the block and return, only to enter several paces behind Rudd. The woman turns out to be the owner. Whoever hoisted the table is gone, fired moments before.

"And he was shouting! It is 11am and he is drunk! Paul, would you have defended me?" she asks in mock distress. Smiling his "I know what you mean" smile, Rudd nods: "I would have had your back." "Thank you, Paul," the owner says, making it clear that Rudd is a regular.

The airy, whitewashed restaurant is tasteful, but still a local joint. After we sit down, Rudd smiles less strategically and says: "I'll be straight up with you. I don't know if I would have stepped in if I saw that. But I might have signed a headshot for him."

Rudd, at 44, looks exactly like Rudd the actor who has made his living as Hollywood's go-to guy for buddy movies and bromances. He's about 5ft 8in and solid, like he could lift heavy items (even a drunken employee), but not as if he spends hours at the gym. He is dressed like a member of every third band I saw in the 90s: plaid button-down over a white T-shirt, blue jeans ripped open at both knees, and Blundstone boots. He is both square-jawed and soft, like he could both seduce you and help with the broken toilet in the morning.

If you didn't know him as Phoebe's boyfriend in Friends that may be because you spent a lot of time overwriting that fiction with the scenario that you two finally met and bonded over, well, everything, becoming that worthy lover he's always deserved. There's a reason that there is a Dear Paul Rudd tumblr and not a Dear Cillian Murphy tumblr. Rudd seems like the one who got away, even if he was never anywhere nearby.

But he feels close, and familiar, onscreen. "When I was starting off and I was meeting casting people or directors there was always some comment that I wasn't dangerous in any way," Rudd says. "That's not who I play. I want characters to be relatable. When somebody's watching I want them to feel: 'I know what that's like, because I sense that in myself', as opposed to thinking: 'I don't know how to do what this guy is doing.'"

Rudd's most recent film appearance is as Alvin, in Prince Avalanche, a small film about two lost souls who may just be losers, painting lines on a highway bordering a swath of burnt-out forest in Texas. It's directed by David Gordon Green, whose 2008 Pineapple Express is exactly the kind of stoner-buddy comedy that might have featured Rudd (it didn't). Prince Avalanche, however, is loosely based on an Icelandic film, and nothing like Pineapple Express – or any of those Judd Apatow franchises such as This is 40 and Knocked Up that made Rudd our biggest crush. Instead, Rudd dials down the charisma and becomes terrifyingly mortal .

Alvin wanders the highway with a sad moustache and his girlfriend's little brother, played by Emile Hirsch, taking everything too seriously, especially himself. When Hirsch's character points out that Alvin isn't getting much out of his relationship with his sister, Rudd barks back with a sense of unearned wisdom: "It's called love." The film is full of failed exchanges, each less useful than the yellow line they're painting. It's Waiting for Brodot, and the best part is watching the impossibly likable Rudd bear down, trying to make Alvin more than just a guy covered with ashes going down an endless road.

On the road: Paul Rudd (right) with Emile Hirsch in Prince Avalanche. Photograph: Rex Features

This is darker than Rudd usually gets (on film at least – a Broadway appearance last year featured him as a highly strung evangelical who murders his wife and neighbour). And though Prince Avalanche desperately needs a forest fire – or James Franco stealing the pickup truck while wearing a bear suit — it is worth your time just to see Rudd stripped of his comic tools, working to make us not give up on Alvin.

I ask him if he minds not getting the extreme gigs, the starving madman roles that go to Daniel Day-Lewis and the Oscar squad. "I never wanted to be on the outside," he replies. Rudd's parents were originally from London, and his father was a TWA employee who moved around America but kept a semi-permanent base in Overland Park, Kansas. Rudd developed coping mechanisms early. "My desire to fit in was just as real as anybody else's. All of the moving around, having parents from London, always being in new schools, I felt like an outsider. I just tried to empathise with people's anguish or angst or whatever it was. If somebody was a bully, I would always try to think about why they were the way they were. It didn't mean that I liked them. I just kind of sympathised with people."

It is hard to find someone who doesn't sympathise back. When I informally poll friends on what to ask the actor, three women want to ask if they can have sex with him, and two ask me to give him a script. When I ask a film buff what he thinks of Rudd, he says: "I love Paul Rudd. All gay men love Paul Rudd. It's a rule." I present this to Rudd, who laughs and asks if there was any overlap between those who wanted sex and those who wanted to start filming. "It would just save time."

Don't get any ideas – Rudd has been married for 10 years, has two small children, and is based in Greenwich Village, where he's lived for roughly 18 years. He moved to New York in the 90s after a summer at Bada, the British American Drama Academy, and his aims were, from the beginning, practical. "I always wanted to get enough of a foundation where I felt that I could sustain a career – I wanted a slow burn. I knew that I wanted to be a working actor; I wanted to do things I liked and feel as if I knew how to do it."

'Acting is like yard work – you’re doing it in pieces. Then you look back and you’re like: "I mowed a whole lawn": Paul Rudd with his wife, Julie Yaeger. Photograph: Rex Features

One thing that sustained Rudd between films – where he usually played supporting parts, not leads – were the theatrical stints that grounded him in steady work and kept him out of LA. After his first major role in 1995's Clueless – Rudd plays a stepbrother who acts as the Greek chorus to Alicia Silverstone's Cher, constantly mocking the acquisitive high-schooler and ultimately, yes, getting with her – Rudd returned to New York to spend almost a year working on The Last Night of Bally- hoo, a play by Alfred Uhry, best known for Driving Miss Daisy.

He lights up when we talk about Stanley Tucci and Giancarlo Esposito, both working the New York theatre scene in the early 90s. "I wanted to emulate those guys. I loved them. And David Strathairn is one of my favourites. I always liked the utility player, the guy who shows up, does the job and is great, sometimes not in the showiest role." Rudd talks cheerfully but steadily, as if he's neither reciting boilerplate nor overly impressed by his career. He talks openly in terms of acting as a job. There is no closet Brando in Rudd, a visionary waiting to impale himself on the perfect role and then retreat to a bunker. Rudd wanted in, and he got in.

And while Rudd may not always be the centre of attention, his appealing nature and ability to channel the energy around him has made him a brilliant comic foil, starting with the cult film Wet Hot American Summer in 2001 and 2004's Anchorman, which solidified his relationship with producer Judd Apatow. "They're the only two scripts I sort of kept around to read just out of pleasure," he tells me. "When I met [Anchorman director] Adam McKay, he said: 'I know you can do comedy.' But it was not my background. I did not do Second City or sketch comedy. Then I met Judd, and he was doing 40-Year-Old Virgin and then Knocked Up, so I started working with a lot of the same people."

By the book: Paul Rudd with Alicia Silverstone in 1995’s Clueless. Photograph: Rex Features

This December, we'll see him reprise his Brian Fantana alongside Will Ferrell's Ron Burgundy in the much-anticipated Anchorman sequel. The idea of being a straight man reacting to the crazy draws out Rudd's rhapsodic celebration of early David Letterman. "Letterman? What that guy means? He changed the entire sense of humour in the States. I'm a fanatic. I joined two fan clubs in my life, and his was one of them." What was the other one? "The Proclaimers." My crush on Rudd falters, but we recover.

Like a Paul Rudd character, Rudd keeps not talking about Rudd, not out of avoidance but because he seems to assume you've seen the Apatow hits and, y'know, how much explanation do comic blockbusters need? He gets excited again when we bump into the fact that he is tied to celebrated rock music, albeit sideways. As we walk away from the restaurant, he looks up an interview (with himself) on his iPhone and announces his musical credentials: "Yup, two Radiohead songs in both 'Clueless' and 'Romeo and Juliet', back when all anybody knew was 'Creep'. I had nothing to do with that, but I'm still really proud of it."

I leave him with my own embarrassing bit of gushing about Party Down, the cult TV series he co-created and which will soon be a feature film. A magical two-series wonder about a half-dozen misfits in LA who cater parties while irreparably fluffing their acting and writing careers, it drew in part on Rudd's own experience of MCing at bar mitzvahs, although Rudd remains shockingly low key about the role he played in it. His original idea of being what he describes as a "viable" employee, a favourite word, still obtains. "I've worked steadily for a good number of years now, and it's like yard work, where you're doing it in pieces. When it's all done, you look back and you're like: 'Oh look, I mowed a whole lawn. When did that happen?' I ask him how many lawns he thinks he's mowed. "I've mowed a couple of plots of land."

Prince Avalanche is in cinemas 18 October. Anchorman 2: The Legend Continues is out in December