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KRISTEN, RUPERT & ROBERT
The rumors: Kristen Stewart and Robert Pattinson's three-year relationship was rocked by scandal in July 2012 when Stewart admitted she'd cheated with her married Snow White and the Huntsman director, Rupert Sanders.
The aftermath: K-Stew issued a public apology to her Twilight love, and Sanders also apologized to his wife, actress-model Liberty Ross, and their two children. After a two-month break, Stewart and Pattinson reconciled and seemed back on track, with the pair most recently celebrating Stewart's birthday together in April and even holding hands at Coachella. But things took a drastic turn weeks later, with sources confirming to PEOPLE on May 18 that the couple has called it quits – for now.
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LEANN, DEAN, EDDIE & BRANDI
The rumors: Not long after married country star LeAnn Rimes began filming the 2008 Lifetime movie Northern Lights with married actor Eddie Cibrian, stories circulated that the two were having an on-set affair.
The aftermath: Rimes and Cibrian both ended their marriages (hers to dancer Dean Sheremet and his to Brandi Glanville of The Real Housewives of Beverly Hills) and eventually wed each other. Later, Rimes publicly bore the blame for hurting people, but added, "I don't regret the outcome."
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RUSSELL, MEG & DENNIS
The rumors: The New Zealand bad boy and America's Sweetheart were thrown together on the set of the 2000 romantic drama Proof of Life, where photographers captured the pair's public displays of affections on location in Ecuador and later, in London.
The aftermath: With British tabloids set to break the story of the relationship, Ryan and her husband of nine years, Dennis Quaid, announced their split, though denied any third party was involved.
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ELIZABETH, EDDIE, RICHARD & SYBIL
The rumors: The late Elizabeth Taylor had already been labeled a homewrecker when the recent widow had married her best friend Debbie Reynolds's husband, Eddie Fisher. Now married to Fisher, the icon started an affair with Richard Burton, her costar in the 1963 epic Cleopatra, and set off firestorm that even had the Vatican weighing in.
The aftermath: Taylor and Burton's on-set affair proved to be the start of one of the great Hollywood romances. They left their spouses (he'd been married to actress Sybil Williams since 1949) and then married each other, a fiery union that lasted 10 years before the duo split, then remarried briefly 16 months later.
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ANGELINA & BILLY BOB & LAURA
The rumors: Angelina Jolie and Billy Bob Thornton played a couple in the 1999 movie Pushing Tin, then suddenly eloped in Las Vegas in 2000, shocking everyone – including Thornton's fiancée at the time, Laura Dern, who said: "I left our home to work on a movie, and while I was away, my boyfriend got married and I never heard from him again."
The aftermath: The pair called it quits three years later, but remain friends. He's sworn off marriage, but Jolie recently got engaged to longtime love Brad Pitt.
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CLAIRE, BILLY & MARY-LOUISE
The rumors: In 2003, Billy Crudup was expecting a child with Mary-Louise Parker, his girlfriend of eight years, when reports surfaced that he was secretly dating his Stage Beauty costar Claire Danes – a charge his reps vehemently denied.
The aftermath: Two months before Parker gave birth to the couple's son, Crudup officially ended their relationship and began dating Danes. "That was a choice I made to fall in love," Danes later said of the timing of the romance, which lasted four years. "It's unpleasant to be cast in such an unflattering role, but I just had to remain steadfast."
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CHAD, PARIS, NICK & SOPHIA
The rumors: Chad Michael Murray was married to One Tree Hill costar Sophia Bush when reports surfaced that he was cheating on her with Paris Hilton, his costar in the 2005 horror movie House of Wax. (Hilton was at the time in a relationship with boy bander Nick Carter.)
The aftermath: In 2005, Bush ended her five-month marriage, citing fraud as grounds for an annulment. In 2011, Murray told E! Online: "I don't do any of those things anymore … When you're young and you're thrown into something that I was definitely not ready for – I'm human and screw up."
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MICHELLE, JOHN & GLENNE
The rumors: John Malkovich had been married to Glenne Headly for six years when sparks flew for real between him and Michelle Pfeiffer, who played his character's saintly love interest in 1988's Dangerous Liaisons.
The aftermath: Malkovich and Headly divorced in 1988 and Pfeiffer married television hit-maker David E. Kelley in 1993. "It's hard to believe Michelle Pfeiffer ever said hello to me," Malkovich said 20 years after the real-life dangerous liaison.
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CYBILL, PETER & POLLY
The rumors: Critically lauded director Peter Bogdanovich fell for 21-year-old model-turned-actress Cybill Shepherd while they were making The Last Picture Show in 1971. He left his wife of nearly a decade, producer Polly Platt, who had discovered Shepherd and insisted on casting her in the lead role in the first place.
The aftermath: Shepherd and Bogdanovich dated for seven years, and in the mid-'80s Bogdanovich even joked about their affair when he made a cameo on Moonlighting. The twice-divorced Shepherd recently announced her engagement to jeweler-turned-psychologist Andrei Nikolajevic.