NEW YORK (Reuters) - A comedian, a millionaire and an orangutan. It may sound like the beginning of a screwball joke, but Donald Trump isn't laughing.

The famously outspoken real estate magnate has sued famously outspoken television host Bill Maher, demanding the $5 million Maher offered to give to charity if Trump could prove his father is not an orangutan.

But legal experts say Trump is unlikely to get a dime from Maher, the host of the HBO series Real Time With Bill Maher, because his offer was clearly made in jest.

"It's parody," said Bryan Sullivan, a Los Angeles entertainment lawyer. "You know Bill Maher is a comedian and a satirist. The offer is so ridiculous."

Trump, however, has taken the comic at his word.

"Attached hereto is a copy of Mr. Trump's birth certificate, demonstrating that he is the son of Fred Trump, not an orangutan," Trump's lawyer, Scott Balber, wrote to Maher last month.

When Maher did not respond, Trump filed a breach of contract lawsuit last week in Los Angeles Superior Court.

A Maher spokeswoman referred to his show Friday, in which he ridiculed Trump's lawsuit.

"It's never a joke when someone reneges on a commitment that benefits worthy charities," said Michael Cohen, special counsel to Trump, in response. "The tone of Mr. Maher's diatribe on Friday evening suggests he is far more concerned with the lawsuit than he wants the public to believe."

Last year, during the presidential campaign, Trump offered to give $5 million to charity if President Barack Obama would release his college records. Trump, who flirted with a possible White House run, previously questioned Obama's citizenship and boasted that he prompted Obama to release his birth certificate.

As a guest on NBC's The Tonight Show last month, Maher offered to give $5 million to charity if Trump could prove he was not the son of an orangutan, since the ape's orange fur matches the color of Trump's trademark gravity-defying coiffure.

"He can donate to a charity of his choice," Maher said. "Hair Club for Men; the Institute for Incorrigible Douchebaggery. Whatever charity."

Under contract law, a verbal offer can create a contractual obligation. But courts make exceptions for obviously satirical offers.

In a New York federal case, Leonard vs. Pepsico, a man sued the soft drink maker after it refused to honor a TV advertisement "offer" of a fighter jet for redeemable Pepsi Points.

District Judge Kimba Wood in Manhattan said an offer made "evidently in jest" is not a contract and noted the commercial featured a teenager using the jet to get to school.

"This fantasy is, of course, extremely unrealistic," Wood wrote.

Trump's lawsuit alleges that Maher's show is political commentary, not comedy. In a Fox News appearance last week, Trump said he was certain Maher's offer was not a joke.

"That was venom," Trump said. "That wasn't a joke."