Robert Downey Jr.

Over the past two weeks, a little-known Hollywood gossip site called Crazy Days and Nights — or CDaN, as it’s known among fans — attracted mainstream media attention when readers began speculating that a commenter known as “Himmm” was actually Robert Downey Jr. The story caught on, spreading to sites such as Gawker, then to cable and entertainment news.

If this were true, it would be a first: a member of the Hollywood establishment turning on his own, revealing the subjects of old Hollywood gossip involving an aging matinee idol, a deceased movie star and a brutal rape. (Allegedly!)

Then, last week, the anonymous blogger behind CDaN — he says he’s a dialed-in entertainment lawyer and goes by the handle “Enty” — posted a blind item that purportedly came from a star of “The Hunger Games,” revealing drug use and bed-hopping: “From day one I knew this actor wanted me,” it read. “So, after a few days of flirting on the set a million miles from our partners, we decided f– – it and we f—ed. Like crazy. Like rabbits.”

Readers guessed that the tidbit could only have come from Jennifer Lawrence, and like so much of what lives on CDaN, trying to determine the truth is akin to proving a negative: impossible.

CDaN almost never elicits reactions from stars. As one high-profile publicist says, “‘It’s the whole ‘I don’t beat my wife’ thing. You really can make something worse.”

In Downey’s case, however, his publicist issued an outright denial, and speculation moved along. But what most everyone in Hollywood wants to know is: Just who’s behind Crazy Days and Nights, and how can he be stopped?

“People have always asked me, ‘What is it with this guy, the sketchiness around his identity?’ ” says one veteran show-business reporter. “It’s interesting how scared people are.”

The blog’s author — who is, ironically, obsessive about his privacy, — agreed to speak with The Post on the condition that we not reveal his identity or place of business.

Online, Enty writes that he’s an obese, thrice-divorced entertainment lawyer who lives in his parents’ basement, drinks heavily and networks with his famous clientele, who feed him his best items. Only some of this, he says, is true.

“I am not 400 pounds and living in the basement,” he says, laughing. He began the blog as a hobby; a few years ago, he tells The Post, Gawker Media offered to buy his site.

He says that some of his best stuff comes from celebrities he’s been friendly with — Leonardo DiCaprio, for example, the subject of one of his recently revealed blinds. Enty also says he was friends with actress Amber Tamblyn when she lived in LA, and sent along a poem and a 2007 handwritten FedEx receipt supposedly from Tamblyn as proof.

The veteran showbiz reporter believes that the RDJ scandal has led Enty to ramp up his blinds and, by extension, unique hits. “That’s the only way to make money,” she says.

“But the culture has become so damaging that someone who leaves anonymous comments can drive the story,” she says. “What kind of world is it that someone can just claim one star raped another?”

Enty says he’s not out to defame anyone: “I don’t reveal things that make people look really bad.” He has integrity and expects the same: “In the industry,” he says, “only five people know who I am.”

So just who is “Enty?” He provided The Post with a scan of his bar card, and he is, in fact, a lawyer registered with the California Bar. According to public records, he is 43 and lives in Los Angeles.

He does work at an LA-based law firm but according to them, he’s not an entertainment lawyer — they don’t even have an entertainment division. Enty, it turns out, handles wills and probate.

Nearly everything Enty says, in fact, doesn’t check out. That package Tamblyn sent? That receipt, dated December 2007, came from an LA-based recording studio called Michael Turner Productions; sole employee Michael Turner says Tamblyn has never been through there: “What does she do?” he asks.

Gawker Media, says founder and CEO Nick Denton, never offered to buy CDaN.

Oh, and the person most likely to be Himmm, according to Enty? Someone who tells the Post he’s shocked to hear it — absolutely not true; he lives in Virginia and has retained a lawyer.

It all indicates that Hollywood and the media have been punked — duped by a soft-spoken probate lawyer with delusions of grandeur.

And he’s only getting bolder, accusing aging and dead stars of a rape, murder, pedophilia.

So, why hasn’t he been sued yet?

‘Our jobs are hard enough without the fracturing caused by the Internet,” says one LA-based lawyer, who represents an Academy Award-winner. “With an anonymous gossip site, you have to find out who registered it” — Enty’s domain is hidden — and even then, the address could be hopping from computer to computer. Given that news lasts five minutes these days, sometimes the advice is: Don’t do anything.”

And if a celebrity did sue, the onus would be on them: They’d have to prove that the information was not only false but posted with malicious intent, and invite high-profile media coverage that would last longer than the most outrageous online rumor.

And so, until libel laws catch up with the web, Enty will probably continue to “reveal” the “answers” to his scandalous blinds, celebrities and publicists afraid to deny them. Because, as one publicist says, “If I go on the record to say my client doesn’t know him, who knows if he’ll get mad? And what will he say next?”