During Gellar's appearance on The Talk Thursday, O'Connell, 47, and the actress, 44, discussed their long history with one another, revealing that they went to the same high school and later dated one another.
"Apparently, you went to the same high school in New York, you were costars in Scream 2 and even dated for a bit," co-host Amanda Kloots said. "Now, we've all seen the friendly, energetic energy that Jerry is now but we can't even imagine, Sarah — what was he like in the 90s?"
Gellar, in turn, said that The Talk cast is "getting the more subdued, calmed down" version of the newest co-host.
"You're getting the more mature, fatherly Jerry. The 'lessons learned' Jerry," she continued. "I had the actual energetic Jerry."
The former Scream 2 costars attended the Professional Children's School in New York.
"I was a freshman, he was a senior. He never acknowledged me," Gellar recalled of their time in school before directing her attention to O'Connell, "You never acknowledged me in school. It was only later that you would actually talk to me."
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Asked about whether O'Connell was "the cool guy on campus," the Stand by Me actor said: "Listen, I was a senior. I didn't want to come off as, like, too much of a predator. I respected age differences and everything."
"By the way, this is not a filter. You have never seen me blush as much as I have on this show [today]," he said before telling Gellar, "You look beautiful. I'm so happy for you."
Though Gellar and O'Connell didn't confirm the duration of their relationship, they were previously photographed attending the 1998 Emmy Awards together. At the time, Gellar was 21 and starring in Buffy the Vampire Slayer while O'Connell was 24 and starring Sliders.
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Now, Gellar is married to frequent costar Freddie Prinze Jr. The longtime pair, who wed in 2002, are parents to daughter Charlotte Grace, 11, and son Rocky James, 8.