"We were at a wedding together and I was like, 'Oh, my gosh, do you and your fiancè [Anna Marie Tendler] want to go have dinner or something and go hang out?" Munn, 40, told HuffPost Live in 2015.
"At first, it was cool and then I kept going up to him at the wedding like, 'So you having fun?'" she continued. "I was just so obsessed with hanging out with and talking with him."
Munn said that she sent Mulaney, 38, an email after the wedding but claimed that "he never emailed back." The Newsroom alum added, "I might've got the wrong email — probably. That's what I tell myself."
PEOPLE broke the news about Munn and Mulaney's relationship on Thursday.
"This is very new, they're taking it slowly," a source close to the former Saturday Night Live writer said. "They met at church in Los Angeles."
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Months before the coupling was reported, Munn publicly supported Mulaney as he entered rehab late last year after relapsing following a struggle with addiction.
"Sending SO MUCH love and support to John Mulaney," she tweeted in December. "You got this. ❤️⚡️."
In February, the Big Mouth star completed his 60-day rehab stint and is continuing to work on his sobriety as an outpatient.
PEOPLE confirmed on Monday that Mulaney and wife Anna Marie Tendler, 35, have called it quits after six years of marriage. "John will not have any further comment as he continues to focus on his recovery and getting back to work," the actor's rep said in a statement to Page Six,
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In a statement obtained by PEOPLE, Tendler showed her support for Mulaney in his recovery journey: "I am heartbroken that John has decided to end our marriage. I wish him support and success as he continues his recovery."