In the late 1990s, if Robert Downey Jr. rolled up to an interview at one of Beverly Hills' best hotels dressed in purple striped pyjama pants and his hair wild, you'd presume he was on one of his drug-fuelled benders that had him in and out of rehab. But, on this recent day, Downey is stone-cold sober.

"They're from Barneys," says the 45-year-old actor while tugging at his duds, from the upmarket US department store.

The purple pyjama pants are one piece of a fashion mish-mash Downey has presumably picked up off the bedroom floor and put on for this interview, with a navy blue tracksuit top over a crumpled grey T-shirt, blue joggers on his feet and a black fedora with mauve ribbon on his head. Under the hat, long, wild, unbrushed hair pokes out.

"You don't like it?" he says, offering one of his trademark, stone-faced looks as he runs his hand down his ensemble.

"It looks great," comes the reply.

Laughter ensues, and why shouldn't the somewhat eccentric Downey be giggling? The actor reined in the drug demons that almost destroyed his life and made him unemployable in Hollywood and is now on top of the industry's acting pile, headlining two separate blockbuster movie franchises - Iron Man and Sherlock Holmes - that pay him at least $10 million a film. Last year the stiff suits that make up the Academy of Motion Picture Arts and Sciences welcomed Downey back into the fold, nominating him for his complicated but hilarious Aussie and African American-accented role in the action-comedy Tropic Thunder.

Next up for Downey is Due Date, the new comedy from The Hangover director Todd Phillips and featuring a cast of Jamie Foxx, Juliette Lewis, Michelle Monaghan and another Hangover alumni, Zach Galifianakis.

On the home front, Downey just celebrated his fifth wedding anniversary with one of Hollywood's most influential players, executive producer Susan Downey. Perhaps explaining why his scruffy appearance makes him look as though he has just rolled out of bed for this morning interview, Downey tells how he and Susan have baby-making on their mind.

Downey has one child, 17-year-old son Indio, with ex-wife and former Elite model Deborah Falconer, and he reveals in his typical nonchalant way that now is the right time to procreate.

"Here's the thing," he says, bringing his hands together as if he is about to crack all 10 knuckles. My kid Indio is in his last year of being a minor, he is almost 18. I'm 45, the missus is turning 37 and is super hot. I'm not as hot as what I used to be. I would like to knock her up and try it all over again."

Hollywood's top-tier actors, thanks to global shooting schedules, often have a problem being on the same continent as their spouses, however, Downey and his better half do not have to worry about that. She is the executive producer of the Iron Man and Sherlock Holmes films and sequels, as well as Due Date.

In Due Date, Downey plays uptight, short-fused architect Peter Highman, who is expecting his first child with wife Sara (Monaghan). Several days before Sara is due to have a scheduled cesarean section in Los Angeles, Peter, in Atlanta for a business meeting, boards an LA-bound flight. His short temper and a run-in with Ethan Tremblay - an extremely odd, wannabe actor in tight jeans and permed hair whose dream is to be cast in the sitcom Two and a Half Men - result in both men being thrown off the plane, placed on a no-fly list and forced to drive together from Atlanta to LA before Sara gives birth.

After the $480 million box-office success of The Hangover, the most successful R-rated comedy of all-time, director Phillips had his pick of films and actors for his follow-up. To play dimwit Tremblay, Phillips went with chubby, bearded, stand-up comedian Galifianakis, who stole plenty of laughs in The Hangover. Using his newfound status in Hollywood, Phillips went after Downey for the role of Highman.

Downey, coming off shooting Iron Man 2, did not know if he wanted to jump straight back in front of the camera, particularly with the long Due Date road shoot schedule that took the actors and crew from Atlanta in America's deep south, to Texas, New Mexico, the Grand Canyon, Las Vegas and Los Angeles.

The role of uptight Highman included scenes that are classic, shocking, R-rated Phillips humour, with the character spitting on a dog and punching a young boy.

"I had just done Iron Man 2 and thought 'God, I really need a break', but then I was just drawn to working with Todd and Zach," Downey explains. It always starts with the director and Todd is so smart and confident, self-admittedly wicked, but he's also endearing. He has a great eye and ear for what people think and what is new, fresh and what people respond to."

As Downey always does, he took the character of Highman and put his own spin on it. He turned the character from a straight man into a volcano.

"I don't think Peter was written as some simmering rage-aholic," Downey says. "It just played better off Zach's character to be someone really reactive to these things and, also, I was just thinking on everyone's behalf who has ever been stuck with a moron, how tough it is. It is kind of like parenting."

It was not important that Downey and Galifianakis built up a warm chemistry as their characters are at each other's throats during the movie. Galifianakis says Downey took one fight scene too far.

"Oh yeah," Galifianakis says, recalling the tiff. "There was some physical stuff we did that I felt he went too far with. The scarf I was wearing, he was using it to choke me in a scene and he was really choking me."

Asked about it, Downey laughs.

"Ah yes, he got a little bit fed up," Downey says. "There was a minute where he needed his space. Things had got a little toxic. But, here's the thing. If you are being choked by your own scarf, and just several scenes earlier your character is told you will be choked by your own scarf, when you feel the scarf tightening you need to get a few fingers in it to save your life out of reflex."

The moral of Due Date could be no matter how odd, frustrating and different two people are, they can learn from each other. It is something that leaped out of the page at Downey when he first read the script.

"Yes," he says. "It's always projection isn't it? Here's what I've noticed anyway. Anything that I find distasteful in someone else is something I tend to unconsciously not like about myself and I project it on that person so they mirror it back to me. In some cases you go, 'Why would I want to look in this mirror? It is so annoying and so exhausting'. I'm one of those people too. I can be so annoying and so self-centred and so faultless and I can endanger the safety and well-being of others if I'm off on some trippy thing, but we all can."

Despite his pyjama pants and scruffy hair poking out of the fedora, Downey seems in control of his life. The days of drug abuse are far behind and the best directors, screenwriters and biggest studios are throwing eight-figure sums at him to sign on to their films. He reportedly earned $12 million for Due Date and, along with the Iron Man and Sherlock Holmes sequels. Downey is enjoying the ride, stable home life, being a dad to Indio and is looking forward to hopefully being a father to another bundle of joy.

"I wouldn't wish some of it on an enemy, but I do not regret the past or wish to shut the door on it," Downey, looking back on the highs and lows of his life, says. "If you told me the stuff that I would have to go through to get from A to where I am now aged 45, I would say that is out of the question. There's no way I'd go through that. It is a cosmic joke. But, as I sit here today reflecting on it, I can see there's something divine about it and it kind of tickles me on days that I'm not a miserable prick."

* This article was also published in Courier Mail (AU) on November 20, 2010.