"I don't think Ewan is as proud of his penis as most men who are as well-hung would -- or should -- or could be," Farrell jokes to the magazine. "I think that's the greatest demonstration of his innate humility, that he doesn't wear it like a badge of honor."
Ewan, 43, is looking as handsome as ever on the cover of Nylon Guys, in which he also opens up about hanging with A-listers Angelina Jolie and Jude Law in the late '90s in London, when the actors were all on the brink of hitting the big time.
But you'll have to settle for using your imagination when it comes to the admittedly wild times they had.
"Jonny and Angelina were shooting Hackers, Jude had done Shopping. I'd done Shallow Grave," he recalls, referring to Angelina's first husband, actor Jonny Lee Miller. "We were all kicking off. It was happening. We were having a right laugh. It’s the '90s in London. It was quite fun … That's all you’re getting.”
These days, Ewan has settled down, and has four daughters with his wife Eve Mavrakis, a French production designer.
"I've been a dad for 18 years. Your work reflects your life, and the biggest element of my life is that I’m a dad," he says. "That’s the most important thing of all."
But will he ever reprise his famous Trainspotting role? Ewan teases that a sequel to the memorable 1996 film is "quite real."
"He's now a Glaswegian running a gym in Amsterdam," McGregor laughs, referring to his role as drug addict Renton. "I haven't seen a script or anything. But it seemed to be quite real. I spoke to [director] Danny [Boyle] about it. I met him randomly in a restaurant [last year] before he went up to Scotland to sit with our writer John Hodge and Andrew Macdonald, the producer."