HBO comedian Bill Maher on Monday mocked Donald Trump's absurd offer of $5 million if President Barack Obama could prove that he was a U.S. citizen by pledging $5 million to the "Hair Club for Men" or "Institute for Incorrigible Douchebaggery” if the billionaire could simply provide evidence that his mother didn't have sex with an orangutan.

In an interview on NBC's Tonight Show, Maher told Jay Leno that he was glad Trump "lied" and never kept scheduled appearances on his HBO show "because he turned out to be such a terrible racist."

"I'm not looking for a feud with Donald Trump and I certainly wish only the best for syphilitic monkey who does his Twitter feed," he explained.

Maher recalled that Trump had been outraged when he first parodied so-called truther concerns about Obama's birth certificate by suggesting the reality TV show star's hair color it possible that his father was an orangutan.

"Suppose that perhaps Donald Trump had been the spawn of this mother having sex with an orangutan," the comedian continued. "I'm not saying it's true, I hope it's not true -- but unless he comes up with proof..."

"I'm willing to offer $5 million to Donald Trump that he can donate to a charity of his choice -- Hair Club for Men, Institute for Incorrigible Douchebaggery -- whatever charity."

After the conservative billionaire made his $5 million offer to Obama last year, Comedy Central host Stephen Colbert also vowed to donate $1 million "if you will let me dip my balls in your mouth."

Watch this video from NBC's Tonight Show, broadcast Jan. 7, 2013.

(h/t: Mediaite)