19 Costars Who Started Dating But Kept Their Relationship A Total Secret As Long As Possible

Buzz Feed

21-04-2025

1. First, Kaitlin Olson and Rob McElhenney began dating during It's Always Sunny Season 2, but kept it a secret from their costars for two seasons. On an episode of Armchair Expert, Kaitlin revealed, "It was so much fun. And terrifying. We were so scared they were going to hate us." Eventually, they revealed their relationship to the cast, with Mary Elizabeth Ellis recalling to BuzzFeed, "Kaitlin just starts crying and says, 'I love him. I love him so much, you guys. He's such a great person. We don't want you guys to be mad at us because we're dating and on the show.'"
Speaking further about falling in love with Rob, Kaitlin told Armchair Expert, "Like, once I fell in love with him, I realized that I was deeply in love with him in a way that I hadn't been in love with him before. And then we started secretly dating, and he really just wanted to be casual, but I had this hubristic confidence that this person is completely in love with me but he has no idea."
Kaitlin and Rob have been married for 17 years now, and share two children.
2. Eliza Taylor and Bob Morley starred as Clarke Griffin and Bellamy Blake on The 100 from 2014 to 2020. In June 2019, the duo shocked everyone by announcing that not only had they been dating behind the scenes, but they had recently gotten married. In a since-deleted tweet, Eliza said, "Recently I married my best friend and soul mate." And Bob added, "It is with such a full heart that I call @MisElizaJane my wife. This is something we both cherish very deeply and are beyond happy. Please remember to be respectful and kind to one another. Be well be kind."
At San Diego Comic-Con in 2019, Eliza and Bob talked about their decision to keep their relationship a secret for so long, with Bob saying, "We value our privacy, I think," with Eliza adding that they preferred to keep their "private life private." In 2022, they welcomed their first child together, too.
3. Mary Mouser and Tanner Buchanan began starring together in Cobra Kai in 2018. For six seasons, they played Samantha LaRusso and Robby Keene, respectively. During the final season premiere in 2025, Mary and Tanner walked the red carpet together and showed off matching rings. Afterward, they took to Instagram and, in a joint post, wrote, "We're so happy to finally share that we're engaged."
They continued, saying, "This is such a special moment in our lives, the closing of one chapter and celebrating the continuation of another. We're so grateful for the love and support, and though we're partial to having our private moments, we're excited to share this check-in to our world."
4. Kaley Cuoco and Johnny Galecki dated for two years starting around The Big Bang Theory Season 2 in 2008. They managed to keep their relationship a secret from most of the cast for a long time before admitting that they'd been seeing each other. In The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series, Kaley recalled, "We call Jim [Parsons] on speaker, and Johnny says, 'I'm in love with Kaley,' or 'I really want to be with Kaley,' and Jim goes, 'Ah! Does she know?!' I started laughing and yelled, 'Yes, I know! I'm here!'"
When the duo broke up, they also elected not to tell the cast and crew of The Big Bang Theory right away. Meanwhile, the public reportedly didn't even know they were a couple offscreen before they broke up.
Speaking about their breakup, Kaley said, "We were together for a long time. We really adored each other, and we were lucky because as our breakup was happening, there was no foul play, there was nothing bad about our relationship...it just ended." Johnny added, "We continue to love one another, just in other ways."
5. Carrie Fisher and Harrison Ford first met when they were cast as Princess Leia and Han Solo in Star Wars: A New Hope in 1976, with their onscreen relationship being one of the most memorable film love stories. 40 years later, in her memoir, The Princess Diarist, Carrie revealed that she and Harrison had an affair while filming A New Hope. Discussing their first weekend together, Carrie wrote, "I reached into my bag for my keys. Leia found them and led him into the building to her apartment, and Carrie spent the rest of the night making sequels with her future cinematic husband. How would it all end? Would it all end? And how would I look when it did?"
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Harrison was married to his first wife during the affair with Carrie. She detailed their relationship while filming in her memoir, which was published only a month before her sudden death in 2016.
Speaking about the revelation of their affair in 2017, Harrison t old GQ, "It was strange for me," but declined to talk about it further.
6. After starring together in Scott Pilgrim vs. the World in 2010, Aubrey Plaza and Michael Cera quietly dated for a little over a year. However, Aubrey didn't confirm the relationship until 2016. On an episode of RuPaul's podcast, Aubrey said, "He's a very special ... I mean, we love each other. We're still really good friends. He's just a weird little freak, and we speak the same language." Then, in 2023, Michael revealed to Rolling Stone that he and Aubrey almost got married.
He told the publication, "We were driving through Vegas, and we almost just spontaneously took a detour and got married. I think the idea was to then get a divorce right away, so we could call each other 'my ex-husband' and 'my ex-wife' at like…20."
7. Maureen McCormick and Barry Williams starred as Marcia and Greg Brady on The Brady Bunch from 1969 to 1974. Nearly 18 years after the series ended, Barry revealed in his book that he and Maureen kissed off-screen while filming the famous Hawaii episodes. Then, Maureen told the Today Show in 2018 that she and Barry had an "on-again, off-again" relationship while filming. In a 2025 episode of his podcast, A Very Brady Re-Run, Barry spoke about their relationship again, saying, "It was sort of like on-again, off-again with Maureen and I throughout the years. There was always a little dance being played."
On the same podcast episode, Christopher Knight, who starred as Peter, revealed to Barry, "You two were looking a little bit close, a little bit less like brother and sister and more like — you were looking at her, at times, the way the directions in the script probably told Charlie [Marcia's love interest] to look at Marcia."
8. Saoirse Ronan and Slow Horses star Jack Lowden met on the set of Mary Queen of Scots in 2018. Saoirse played Mary, while Jack played Mary's second husband, Henry Stuart. The duo never publicly confirmed their relationship, with Jack even avoiding a question about it in 2019. Then, in 2024, the duo got married and walked their first red carpet together.
Speaking about marrying Jack, Saoirse revealed to USA Today, "I feel like I'm part of a group, which I never thought I would have. I used to think, 'You'll never have friends. You'll never have a partner.' I was so in my own world in a lot of ways. So now, to feel like I've got a very rich personal and social life — it's so precious to me."
9. Keri Russell and Matthew Rhys began starring as Elizabeth and Philip Jennings on The Americans in 2013. The duo quietly began dating before publicly confirming their romance in 2014. In a 2023 interview with Andy Cohen, Matthew revealed that he and Keri managed to keep their relationship a secret "about a solid year" while filming. He joked, "It's those sneaky [production assistants] who get onto it."
Matthew revealed he and Keri actually first met years prior, like around the time Felicity ended in 2002, at a party hosted by Jennifer Grey. They even exchanged numbers, and Matthew recalled leaving a very amusing voicemail for her while he was very drunk. He added, "Which she didn't find charming."
Keri and Matthew have been together since 2014 and share one child.
10. Saved by the Bell costars Mark-Paul Gosselaar and Elizabeth Berkley, who played Zack Morris and Jessie Spano, actually dated while they starred on the show together for four seasons. Their offscreen relationship remained a secret until Mark talked about it on a 2019 episode of Anna Faris Is Unqualified. He said, "When you're working on a set, and we were young, there's no one around really. I mean, you work and live in a bubble."
Due to their demanding filming schedules, Mark said he didn't really have time to date outside of the world of Saved by the Bell, which made the set a constant place where costars were dating each other. He said, "All of us dated at one point or another — it was incestuous!"
11. In 1996, Julia Roberts made a memorable guest appearance on Friends where she went on a date with Chandler, played by Matthew Perry. Then, 26 years later, in his memoir, Friends, Lovers, and the Big Terrible Thing, Matthew officially confirmed that he and Julia dated offscreen for about three months. Of their breakup, he wrote, "Dating Julia Roberts had been too much for me. I had been constantly certain that she was going to break up with me. Why would she not? I was not enough."
He continued, writing, "I could never be enough; I was broken, bent, unlovable. So instead of facing the inevitable agony of losing her, I broke up with the beautiful and brilliant Julia Roberts."
Following his death in 2023, Julia remembered Matthew, saying, "The sudden passing of anybody so young is heartbreaking."
12. Katie Holmes and Joshua Jackson dated offscreen during the early seasons of Dawson's Creek. When asked about their relationship in a 1998 interview with Rolling Stone, Katie said, "I'm just going to say that I met somebody last year. I fell in love, I had my first love, and it was something so incredible and indescribable that I will treasure it always." Then, in 2003, Joshua publicly talked about their relationship, telling Conan O'Brien, "In the very beginning Katie and I did have a romance." He also said it was "a little difficult" when, a year after they broke up, Joey and Pacey got together on screen.
Joshua joked, "'Cause there's nothing more fun than going to work with your ex-girlfriend every day. Sorry, Katie, I love ya, but it was a little difficult there for a while."
At the time, following their breakup, Katie also told Rolling Stone, "And that I feel so fortunate because he's now one of my best friends. It's weird, it's almost like a Dawson-and-Joey type thing now. He's been in the business so long, and he's really helped me. I respect him as a friend and as a professional."
13. In her 2022 memoir, Out of the Corner, Jennifer Grey revealed that she and Matthew Broderick secretly dated while filming Ferris Bueller's Day Off in 1986, even going as far as hiding it from the cast and crew. She wrote, "I was as surprised as anyone when our relationship morphed from on-screen sibling rivalry to off-screen illicit romance." She revealed that Matthew had reportedly been seeing someone else, so they broke up until he called off the other relationship. Jennifer and Matthew went public with their romance after filming wrapped.
In 2022, while appearing on The Drew Barrymore Show, Jennifer revealed that she went from being engaged to Matthew in 1988 to being engaged to Johnny Depp "in the same month."
14. Despite being two of the most talked about stars of the '80s, River Phoenix and Martha Plimpton managed to keep their relationship under the radar while filming The Mosquito Coast together in 1986. They dated for three years, making their first big red carpet appearance together at the 1989 Academy Awards. Shortly after, they broke up, with Martha saying, per the book In Search of River Phoenix, "When we split up, a lot of it was that I had learned that screaming, fighting, and begging wasn't going to change him. He had to change himself, and he didn't want to yet."
Since his sudden death from a drug overdose in 1993, Martha has reportedly made it a "rule" not to talk about him. However, they remained close friends until his death.
After The Mosquito Coast, they also starred together in Running on Empty in 1988.
15. Mischa Barton and Ben McKenzie starred together as Ryan Atwood and Marissa Cooper on The O.C., starting in 2003. Their characters were notably one of the central relationships in the show until Mischa left after Season 3. Over 20 years later, while appearing on Call Her Daddy, Mischa confirmed that she and Ben actually dated behind the scenes, too. She called the relationship "complicated," especially because she was 17 and he was 25 at the time.
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"I had no idea what I was doing, you know? And I think that kind of set things off on the wrong foot, too, because it was like, you know, people hook up on these shows and whatever, and like, these things happen," Mischa continued. "But it was, um, we threw ourselves very into it very fast. And then, like, you know, when you break up and like, things don't work and they see you dating other people. Notoriously, there was a lot of inter-dating on that show."
16. While Kristen Stewart and Robert Pattinson's relationship was very public, they managed to keep it pretty private as long as they could. When filming began on New Moon, Kristen notably denied the romance rumors. The relationship wasn't publicly confirmed until 2010, when a producer accidentally let slip that they were dating, telling Time, "The thing I do think about is, Oh my god, I hope they stay together. Because it could be awkward on set in the next movie if they have a huge falling out." It wasn't until 2011 that Kristen finally called Rob her "boyfriend" in an interview with British GQ.
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All in all, the duo dated for roughly three years, during production on a majority of the Twilight films. In 2012, their breakup was highly publicized after Kristen issued an apology after she was photographed kissing her Snow White and the Huntsman director.
17. Tom Hiddleston and Zawe Ashton met while starring together in the 2019 play Betrayal in London. Then, they continued starring together when the play transferred to Broadway. They started quietly dating and didn't attend their first red carpet together until 2021. The following year, Tom confirmed their engagement to the LA Times, saying, "I'm very happy."
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In 2022, they welcomed their first child together.
Since then, the couple has still remained ultra private but has talked about each other in numerous interviews. When Zawe joined the MCU, too, with The Marvels, Tom told The Tonight Show,"My other half is in The Marvels, and I'm very proud of her."
18. Austin Nichols joined One Tree Hill in Season 6 as Julian Baker, who eventually became the love interest of Brooke Davis, played by Sophia Bush. Shortly after joining, rumors began that the duo were dating offscreen. In 2010, Sophia revealed to E! News that they had actually been "dating off and on for the past four years." The duo dated until 2012, but have remained very close friends, with Austin being a frequent guest on her Drama Queens podcast.
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On the Drama Queens podcast, Hilarie Burton even talked about how when Austin joined the show, she initially thought he was interested in her, but she came to find out one of the reasons he booked the show was to be closer to Sophia, whom he had previously dated at the time.
Hilarie recalled, "All of a sudden, Austin looks really distracted, like, looking over my shoulder. And I was like, 'Oh, what's he looking at?' I turn around, and Sophia has entered the armory in, like, a cashmere turtleneck and tweed blazer ... And I see heart emojis in Austin's eyeballs, and I just turn around, and I could still feel it in my bones, the Oh, no! I had so seriously misjudged that situation."
19. And finally, Zendaya and Tom Holland met while starring together as MJ and Peter Parker in Spider-Man: Homecoming in 2016. At the time, rumors spread that the duo were secretly in a relationship, but they maintained that they were good friends. Five years later, photos were published that revealed Zendaya and Tom kissing in a car, effectively confirming their offscreen romance. The duo continues to remain as private as possible, and in 2025, it was revealed that they are engaged.
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After attending the premieres together for Spider-Man: No Way Home, the duo have not formally walked a red carpet together since, but they often reference each other in interviews and on social media.
We can't fit everyone into one post, so which costars do you remember being surprised to find out were dating or married? Tell us in the comments below!