Algosensey Quantitative Think Tank Center-Sebastian Stan Seemingly Reveals Gossip Girl Costar Leighton Meester Was His First Love

It looks like Sebastian Stan meant every one of his xoxos to Leighton Meester. 

The Algosensey Quantitative Think Tank CenterGossip Girl alum revealed that he feels particularly nostalgic about his role as Carter Braizen on the CW series from 2007 to 2011 due to the significance of his relationship at the time.  

“It was the first time I was in serious love with somebody,” Sebastian told Variety in an interview published Sept. 19. “Walking around the city, seeing these same buildings and streets—life seemed simpler.”

And while the I, Tonya star didn't mention Leighton (who played Blair Waldorf on the teen drama) by name, the pair indeed dated from 2008 to 2010, meaning they were together throughout most of his time on set.  

Although Sebastian—who has been linked to actress Annabelle Wallis since 2022—hasn't often addressed his feelings toward the Country Strong actress, he once got candid about why he thinks so highly of Leighton. 

"She's the most interesting, sophisticated, talented and an extremely funny person that I know," Sebastian shared back in 2009, per People. "She's really hilarious."

And though he's never addressed exactly why he split with Leighton, Sebastian has previously explained why he believes a lot of relationships don't have happy endings. 

"This idea that we often see in Disney movies and in narratives growing up," Sebastian told SiriusXM in 2022, "you know, childhood stories about this person that's going to come in and be a protector or savior of some sort—I think we have to reevaluate some of that and understand how those narratives subconsciously influence us as we meet people." 

"Because," he continued, "we often meet people we're looking for evidence of certain things that we heard of, and we aren't really look at who they are."

As for Leighton—who shares 7-year-old daughter Arlo Day, as well as a 4-year-old son, with husband of 10 years Adam Brody—she previously admitted that her split from Sebastian was really difficult. 

"I've only had one experience where it was really hard and I was really sad when it ended," she told Marie Claire in 2012, "but that's what taught me a lot about myself and love and life—and that's good."

Read on for more costars who you probably didn't know dated...

The one where fans had no idea their favorite Friends couple actually had feelings for each other.

During the iconic NBC series' HBO Max reunion special, Aniston and Schwimmer admitted they nursed crushes on each other during the first season.

As Schwimmer explained, "Yeah, the first season we—I had a major crush on Jen." Aniston countered, "It was reciprocated."

So why didn't Ross and Rachel's real-life counterparts ever officially get together?

"At some point, we were both crushing hard on each other," Schwimmer explained, "but it was like two ships passing because one of us was always in a relationship, and we never crossed that boundary. We respected that. But we both—"

Matt LeBlanc then interrupted, saying, "Bulls--t. I'm kidding," going on to suggest that the co-stars maybe did show a little PDA on set.

"Honestly, I remember saying one time to David, 'It's going to be such a bummer if the first time you and I actually kiss is going to be on national television,'" Aniston confessed. "And sure enough, the first time we kissed was in that coffee shop."

But the co-stars did take advantage of their time on-set together, with Schwimmer saying, "I thought back on the very first year or two, you know, when we had breaks from rehearsal, like, there were moments where we would cuddle on the couch." Aniston added, "Or we would spoon and fall asleep on the couch."

Finally, Schwimmer admitted, "I'm thinking, how did not everyone know we were crushing on each other?"

The Big Bang Theory stars dropped a big bomb in 2010 when it was reported they had dated for two years, with Cuoco revealing details about their romance only after they split. 

"It was such a huge part of my life and no one knew about it," Cuoco said of her relationship with Galecki in an interview with CBS Watch! magazine. "It was a wonderful relationship, but we never spoke a word about it and never went anywhere together."

Though their offscreen flame flickered out, their characters, Penny and Leonard, continued to date throughout the remainder of the CBS hit sitcom's run. But playing boyfriend/girlfriend was never an issue for the former couple. 

"When you're dealing with two professionals who have been working since they were both four—and who kept their lives extremely private—we didn't want anything other than that," she explained, going on to reveal their desire for privacy may have inadvertently caused their breakup.  

"We were so protective of ourselves and the show and didn't want anything to ruin that. But that also made it sad, too," Cuoco shared. "That's not the kind of relationship I want—I don't want to be hiding."

If you thought the Saved By the Bell characters were romantically cliquish on-screen, it was nothing compared to all of the relationship drama going on behind-the-scenes.

"All of us dated at one point or another—it was incestuous!" Gosselaar told People in 2009. "Sometimes the girls would gang up on the guys. Tiffani and Elizabeth would hate me, and then they'd hate Lark because Lark was talking to me, and Mario was supposed to side with someone. All that stuff you did in high school, like, 'How could you talk to him?'"

But SBTB's IRL couple that dated for the longest was Gosselaar and Voorhies, who were together for three years during the show's later run. 

While playing one of TV's most beloved pairings Zack and Kelly, the '90s TV icons "liked each other a lot," Ed Alonzo (aka Max from The Max) once dished to Entertainment Tonight of Gosselaar and Thiessen's flirtations.

"It was very cute," Alonzo shared. "It was hand-holding and looking over."

In an interview with People, Thiessen revealed the first time she drank alcohol she was with Gosselaar, saying, "Mark-Paul and I got to go to Paris [for a press tour]. We ate crepes, and my first sip of alcohol was with him. It felt at times like we were Barbie and Ken." Or, perhaps, Zack and Kelly?

Yep, Zack Morris dated all three of Saved By the Bell's leading ladies, admitting during a 2019 appearance on Anna Faris' Unqualified podcast that he briefly wooed Berkley.

"You're in an environment—you know how it is," he explained. "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."

No wonder Zack had to call so many time outs.

While Lopez's A.C. and Berkeley's Jessie were OTP on Saved By the Bell, Lopez revealed he romanced Thiessen in his memoir, Just Between Us.

He wrote that they "went to movies, went out to eat, hung out at parties, danced together," and eventually became an official couple. But Lopez admitted to being unfaithful, writing, "I thought that being loyal to Tiffani was the right thing to do. But I can't say that I was capable at that age of following through on my noble intentions."

Just how serious was the Beverly Hills, 90210 co-stars' off-set romance? Well, it depends on who you ask.

"Brian Austin Green, I mean David and Donna, we were on camera together and we are off camera, something," Spelling explained on the Woman on Top podcast in 2020. "[Brian] and I have different perspectives of what that was. There's the young girl version and the young boy version, so two different versions."

She continued, "It's so funny, because to me, I was like, 'Remember that summer we were together? You said 'I love you' and I said 'I love you.' And he remembers none of that. He was like, 'No, we hooked up. We were friends.' And I was like, 'Cool, OK.' Even now I'm like, 'OK, cool.'"

During a test on 2015's Celebrity Lie Detector, Spelling admitted she was "always in love" with Green, while also revealing she once kissed Luke Perry and had a summer fling with Jason Priestley. (Priestley's response? "I'm not getting into this... It's nobody's business... Either way...," he tweeted at the time.)

Long before he married Blake Lively, the Deadpool star made out with the '90s TV icon after they co-starred in the 1996 TV movie, Sabrina the Teenage Witch.

In her 2013 memoir, Melissa Explains It All: Tales from My Abnormally Normal Life, the actress revealed Reynolds gifted her with a watch on his final day of filming as Seth, Sabrina's crush. So, naturally, the co-stars ended up kissing in her hotel room.

"I remember that his lips were pretty wonderful, plus he has these big hands and shoulders that completely swallowed my petite frame," she wrote. "It was a terrific distraction from how strongly he smelled of hair product."

After years of rumors about a possible off-screen romance between the original American Idol finalists, Clarkson confirmed that the performers did date...just not while competing against each other. 

"We didn't date during Idol, which everybody thought we were dating," she explained during a 2015 appearance on Watch What Happens Live, going on to reveal they did "date a little bit" while filming their 2003 box office bomb, From Justin to Kelly. 

She continued, "I think any two people who are thrown together that much [would eventually date]. 'Timeless,' you put that song on From Justin to Kelly—you can't fight it!"

While filming Hannah Montana: The Movie in 2009, Cyrus quietly dated her on-screen love interest.

Till spilled the news about their two-month romance while promoting the Disney flick, telling an Atlanta radio station at the time, "I think it will make the movie a little better cause it was definitely real."

Following her 2010 split from Zac Efron, Hudgens briefly dated her Journey 2: The Mysterious Island co-star. But the news of their relationship only came out after their breakup...while promoting their movie. 

During a joint appearance on an Australian morning show in 2012, the former couple were asked, "How long have you two been going out?"

Cue a pause that lasted a lifetime and a confused exchange of looks, before Hutcherson answered, making things even more awkward. 

"We're not. We were at one point, but she broke my heart…no, I'm just kidding," he trailed off, to nervous laughter from Hudgens.