They said "I do!" Thomas Sadoski revealed that he and pregnant fiancée Amanda Seyfried got married on Sunday, March 12, by secretly eloping.

The dad-to-be announced their surprise wedding during an appearance on The Late Late Show With James Corden on Thursday, March 16. Watch his sweet announcement in the video above! The Life in Pieces star referred to the Mean Girls actress as "my wife" and held up his hand to reveal a gold wedding band as Corden started to congratulate him on his engagement.

"When did you get married?" a surprised James Corden asked.

"Sunday," Sadoski, 40, replied as the audience responded with applause and cheers.

"We eloped," he continued. "We just took off into the country with an officiant and just the two of us, and we did our thing."

Sadoski gushed that Seyfried, 31, is "the person who I love, admire, respect most in the world."

He added that the intimate ceremony "was beautiful. It was everything that it should be. It was just the two of us talking to each other."

Corden asked what they did after the ceremony and Sadoski answered simply, "Then you take the dog [Seyfried's beloved Australian shepherd, Finn], you walk through the country and you go home. And you, like, have your life."

They also went out to dinner. "It was awesome," he continued. "We had a great day. It was perfect."

Corden then quizzed the newlywed about whether he was ready for the imminent arrival of the couple's first child.

"No," the Newsroom alum replied. "How can you be? I'm more excited about this than I've ever been about anything in my life. And I'm also more terrified about it than anything I've ever been in my entire life. If I'm too confident, then I'm just kidding myself."

Seyfried, who confirmed her engagement to her The Last Word costar in September 2016, teased her new husband's Late Late Show appearance earlier on Thursday, captioning a pic of Sadoski, "This nice man is going to be on @latelateshow tonight to talk about nice things!"

This nice man is going to be on @latelateshow tonight to talk about nice things! 💫

A post shared by Amanda Seyfried (@mingey) on

Want stories like these delivered straight to your inbox? Sign up now for the Us Weekly newsletter!