One of his father’s replacement activities, so it seems, is to follow his son’s mushrooming fame via Google Alert. That is how Fassbender learns much of what is being said about him. A call will come in. Sometimes there are important issues that need addressing. As Fassbender tells me when we meet in New York, "My dad was like, "What’s this about some fan vomiting on your shoes?’ "

In a sane and stable world, this would be a hypothetical example but, surreally, it is not. Since we first met in London, a story had appeared that a starstruck woman was so overcome by meeting Fassbender in a pub near his home that she threw up all over his shoes. A "source" was quoted in one of the British tabloids saying, "He was a bit bemused by his latest encounter and brushed off the vomit and played it cool. He used to be a barman so he’s no stranger to mopping up some sick." Fassbender was particularly surprised by this story (when it was published, friends were sending him texts saying things like "vomit?") for a very specific reason. "I wasn’t there for it," he says. "It just didn’t happen. What are you going to do?"

It was also reported that he got thrown out of his own party following the British premiere of A Dangerous Method. "Another lie," he says. At least he really was there, but he insists that he left of his own accord at 9:45 p.m. "I left early! I suppose ’Michael Fassbender leaves party early’ isn’t as good." In this instance, he seems to take the story as an insult to the times when he has actually succeeded in being ejected: "I have been thrown out of parties, and it’s a different scene than what was photographed that night, I can tell you."

And then there was the biggest Fassbender story of the past few weeks, the joke that never stops, coming round one more time. It was the evening after the comic-book convention in Anaheim, and as usual, his father got in touch: "I see there’s some stuff on the Internet..."

On this occasion the instigator was his Prometheus co-star Charlize Theron. That very afternoon she had spoken to me about him in terms loaded with respect: "The bottom line is, Michael Fassbender is probably the most talented actor that I’ve ever been around, and I think the most talented actor of this time right now.... I cannot talk about Shame because I sound like a fucking freak, but it’s a film that stayed with me for three weeks. His performance haunted me. I watched it twice, and when I look at the nuance, the delicacy, the tenderness, there was nothing heavy-handed about him. He knows what the balance is. He knows real life, he doesn’t know pretend life.... The bottom line is that he should have an Oscar on his mantel right now."

The same evening, Fassbender introduced Theron at a Human Rights Campaign gala in downtown Los Angeles, where she was accepting an award for her humanitarian work. He kept it simple: After a quick apology for being underdressed (jeans, white shirt, leather jacket) and a "Happy St. Patrick’s Day, everybody!" (he came onstage with a tumbler of what appeared to be whiskey), he knelt on one knee to present her with her award. He then retreated to the back of the stage and she took the lectern.

Faced with a restless crowd to entertain and the knowledge that an attractive movie actress talking the right kind of dirty rarely fails—and with the eternal modern alibi that it was all for a very good cause—Theron took the low road with impressive verve. Some words of thanks to her presenter segued into an appreciation of Shame. "As an actor," she started, "I have to say I was truly impressed that you chose to play it big. [laughter] I mean, most other actors would have gone small, trust me. [more laughter] No, I know, because I’ve worked with most of them... [more laughter] No, seriously_ [a nice fake so that the audience now expects sincere human-rights chatter]_...your penis was a revelation. I am available to work with it anytime."

He tells me that from where he was standing he could hear the laughter but couldn’t really hear the words. "I should have known, to be honest," he reflects. "You know, she’s pretty mischievous, and she’s got a pretty filthy mouth. Yeah, I should have been prepared, really. I wasn’t, stupidly enough."

Afterward, Theron said to him, "I hope you don’t mind me making a joke about your penis."

Fassbender told her it was fine. I have no doubt he sort of meant it.

Chris Heath is a GQ correspondent.