Insider – fabled funnyman not laughing when close pal “dopey” LANCE ARMSTRONG confessed his BIG fix!

NO one in Hollywood feels more betrayed by Lance Armstrong than his good pal Robin Williams, who insiders say was stunned when the cycling legend confessed to using performance-enhancing drugs in a bombshell interview.

“Robin’s tried to wrap his head around it and he can’t,” a source told The ENQUIRER. “He feels completely let down.

“Robin’s supported Lance through thick and thin and believed him when he said he wasn’t doping. He bought it hook, line and sinker.”

In 2004, the 61-year-old comedian and actor even wrote the foreword to the book “Lance Armstrong: Images of a Champion.”

“When the doping allegations first surfaced years ago, Lance as­sured Robin others were out to get him and he was telling the truth,” said the source. “Robin didn’t doubt Lance’s word and told everyone the accusations were hogwash. Now he feels like a fool! Publicly, Robin has been silent about the scandal, but privately, he’s fuming. When Lance needed a celebrity for a benefit, Robin was there at the drop of a hat. Now he feels like he’s been stabbed in the back.

“He told a pal: ‘Lance lied to me!’”

The source adds that Williams may even get swept up in Lance’s legal mess.

“Since Robin was so close to Lance, he could be deposed in the multitude of civil lawsuits that are expected to be filed against him. Robin stuck his neck out for Lance, and he was repaid with a bunch of lies.”

Williams was frequently seen by Armstrong’s side when the cyclist competed in the Tour de France, and supported the superstar’s charita­ble causes. Last October, days after Lance stepped down as chairman of his cancer charity Livestrong, Robin, along with Sean Penn and singer Norah Jones, attended the charity’s 15th anniversary at the Austin Con­vention Center. A crowd of 1,700 – including Robin – gave the former champ a standing ovation.

The Livestrong event was Arm­strong’s first public appearance after the United States Anti-Doping Agen­cy (USADA) released a report with evidence of his heavy involve­ment in a doping ring.

After years of denials, Arm­strong finally came clean publicly during an interview with Oprah Winfrey, which aired on Jan. 17. He confessed to “doping” with blood trans­fusions and using banned performance-enhancing drugs, human growth hormone, testosterone and cortisone.

One person who was glad to hear it was Emma O’Reilly, a masseuse and assistant for the U.S. Postal cycling team who blew the whistle on Lance’s drug use in 2004, and says he branded her “an alcoholic whore” because of her revelations.

The confession also prompted his longtime pal, actor Matthew Mc­Conaughey, to say he was “p***** off ” with Lance, telling MTV News: “I was mad. I then got kind of sad for him…fourteen years he lied and carried the lie with him.”

Added the source: “Before his admission, Lance was the toast of Hollywood, dating singer Sheryl Crow and actress Kate Hudson and hanging with several A-list stars. Now that he’s admitted to doping, they’re all staying away from him like he has the plague. He’s become one of the most despised sports fig­ures ever.

“Meanwhile, Robin is trying to brush this whole thing off and act like it doesn’t bother him too much, but it does. It’s crushed him.”