Katharine McPhee Involved in Cheating Scandal; What Other Celebrities Did We Forget Cheated?

Looks like Katharine McPhee's former show Smash was less dramatic than the American Idol alum's real life. McPhee has been spotted kissing Michael Morris, her former Smash director, on the streets of Hollywood. McPhee, who married producer Nick Cokas in 2008, has been separated from her husband for six months, according to reports. Michael Morris, however, is a married man with three children under the age of 10. Yikes!

Whatever the status of both of these marriages, one thing is clear: McPhee and Morris definitely have some explaining to do. But they're not the first couple to get involved in a cheating scandal. Obviously, you remember Tiger Woods, Jesse James, and Hugh Grant's respective illicit affairs, but do you remember these forgotten celebrity cheating scandals?

Marilyn Manson

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Marilyn Manson allegedly hooked up with 19-year-old actress Evan Rachel Wood before he had the chance to divorce his wife, burlesque dancer Dita Von Teese. His turbulent relationship with Wood ended in 2010, but we tend to think both ladies are much better off without the shock-rock singer.

Claire Danes

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The Homeland star not only participated in an illicit affair on screen — with married Sergeant Brody — but off screen as well. In 2003, Claire Danes and Billy Crudup had an affair while Crudup's longtime girlfriend, Mary Louise Parker, was seven months pregnant with his child. After shacking up with Billy, Claire Danes fell for her now-husband Hugh Dancy on the set of their film Evening.

Meg Ryan

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Meg Ryan and Dennis Quaid were married for nine years when Meg Ryan met Russell Crowe on the set of their film Proof of Life. The two movie stars had an affair, which turned into a short-lived relationship. She always seemed a better fit for on-screen paramour Tom Hanks anyway.

Chad Michael Murray

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Remember when Chad Michael Murray reportedly cheated on One Tree Hill co-star Sophia Bush with heiress Paris Hilton in 2006? Maybe, but you'd have to remember why Chad Michael Murray was relevant in the first place.

David Duchovny

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The Californication star cheated on wife Tea Leoni, but it was only because he was suffering from sex addiction, you guys! After a stint in sex-addict rehab in 2008, David and Tea got back together. David should totally write a memoir about the experience and call it The (SE)X Files.

Billy Bob Thornton

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We all remember the infamous Angelina Jolie-Brad Pitt-Jennifer Aniston love triangle, but before Brangelina happened, Jolie was involved in yet another cheating scandal. Billy Bob Thornton was engaged to actress Laura Dern from 1997 to 1999. Then, while Dern was away working on a movie, Billy Bob Thornton hooked up with Angelina Jolie... and subsequently married her, behind Dern's back. Too bad the couple was only Mr. and Mrs. Thornton for three years.