By Marilyn Beck and Stacy Jenel Smith When Naomi Watts and Liev Schreiber joined with Edward Norton to make the big-screen adaptation of Somerset Maugham's "The Painted Veil," Watts and Schreiber had just met. By the time the tale involving a passionate adulterous affair wrapped, they were madly in love. Now they're the subject of "when-will-they-marry?" stories.

That makes them just the latest in a line of stars who first found romance acting together - a line that stretches back well beyond the beginning of cinema. Just to name a few: Brad Pitt and Angelina Jolie, Michelle Williams and Heath Ledger, Jennifer Garner and Ben Affleck, Rachel McAdams and Ryan Gosling, Sophia Bush and Chad Michael Murray, Jennifer Aniston and Vince Vaughn, Dominic Monaghan and Evangeline Lilly, Kurt Russell and Goldie Hawn, Antonio Banderas and Melanie Griffith, Humphrey Bogart and Lauren Bacall.

Tom Cruise (Mimi Rogers, Nicole Kidman, Penelope Cruz) and Julia Roberts (Liam Neeson, Dylan McDermott, Keifer Sutherland) are among the many famous thespians who've have multiple real-life pairings that began as on-set romances.

It almost starts to seem like film and television actors never link up any other way.

Sure, we've all read protests by actors and actresses - especially those who are married or in committed relationships -- about how ridiculous and unfair it is to imagine that just because they play lovers, they'll become lovers in real life. Hey, that's why they call it "acting," right?

But the truth is, it is sometimes difficult for those who portray characters embroiled in intimate relationships not to allow the feelings to seep into their off-camera interactions.

Elizabeth Taylor certainly understood that. She and Richard Burton had already made "Cleopatra," during which they'd fallen in love, when Burton went off to the sleepy seaside hamlet of Puerto Vallarta, Mexico, to film 1964's "Night of the Iguana" opposite sexpot Ava Gardner. Taylor made sure she was right there with him as well. In fact, she would barely let him out of her sight. The fact that he would go off with Ava and the rest of the company to the village of Mismaloya to shoot - a place then accessible only by boat - filled the film queen with frustration. Few of us who were there will ever forget her pacing back and forth on shore, awaiting his return. She repeatedly called Michael Wilding, one of her ex-husbands, who was in Vallarta serving as Burton's representative, via ship to shore radio to ask when Burton was coming back. Meanwhile, Ava, the object of Taylor's fears, was busy being romanced by a couple of tanned beach boys.

Theirs was hardly the only entanglement on the steamy set. Affairs were going on all over the place, it seemed. There was also young Sue Lyon, there with her boyfriend, and lovely Deborah Kerr, accompanied by her husband, Peter Viertel - who was himself a former boyfriend of...Ava Gardner.

Kerr, noting all the pairings, commented on the fact that it felt as if they weren't in the real world, but off in a different place, where it seemed all the rules you normally had to follow didn't apply.

Perhaps that sense of being in a world unto itself provides part of the explanation for Meg Ryan's affair with leading man Russell Crowe while making 2000's "Proof of Life" on locations in London, Ecuador and Poland. The movie depicted Crowe's character being consumed by an inappropriate attraction to Ryan's character, who was married to the man whose kidnapping he was trying to solve. Ryan was still married to Dennis Quaid at that time, you'll recall, and the publicity over Crowe's affair with a married America's Sweetheart is believed to have hurt both the movie's chances (director Taylor Hackford bluntly said just that) and to have done permanent damage to Ryan's career.

It doesn't take being half a world away for the sense of insulation and isolation to kick in - or romance to take over. Then of course, there are the many times when all that love on camera IS just acting.

Patrick Dempsey and Ellen Pompeo, who've been having a McDreamy steamy affair on "Grey's Anatomy," raised eyebrows with cozy poses on a fashion shoot and at an awards show recently - though Dempsey's a very married family man.

Jonathan Silverman and Jane Seymour are playing paramours on ABC's new "In Case of Emergency." As he put it: "Dr. Quinn has joined the cast and jumped in with both feet and other body parts, too. These are surprisingly explicit love scenes for network television. We played two days completely naked."

However, Silverman and Seymour and their respective significant others are incredibly sophisticated about it. Jonathan reported that he and his fianc?e, "Close to Home" star Jennifer Finnigan, and Jane and her husband, James Keach, wound up sitting next to each other at one of the last Dodger games of last season.

"Jane asked forgiveness from Jennifer, and I asked forgiveness from Mr. Keach," recounted Jonathan, "and we're all good friends now."