John Mulaney Jokes Olivia Munn Has 'Cancer Brain' While Discussing Health Battle In New Comedy Special

According to John Mulaney, it's not only very real, but something his wife Olivia Munn experienced while battling breast cancer.

"Yes, I have two children now. One was controversial, one you all seem to be cool with," Mulaney joked during the premiere of his new Netflix talk show, Everybody's Live With John Mulaney, Wednesday.

"So, thank you so much for that. I did want to say something: Over the past few months, many people have reached out in a very nice way about my wife Olivia who's been battling breast cancer," he continued. "I really appreciate all the nice messages that obviously she has received and that even I have received."

"But it's been a real thing to be with someone you love so much going through this," he shared. "In the past couple years, Olivia has had five surgeries, months and months of cancer treatment, and the fight that she's put up has made her so inspiring."

"And the effect of cancer treatment on her brain has made her, at times, so dumb," Mulaney quipped. "There's a thing called cancer brain: not brain cancer. Cancer brain."

As the comedian describes it, "It's a sweet, wonderful dumbness that happens after all that challenging treatment."

Mulaney said he really saw it in action when the pair went to a fertility doctor to make embryos for what eventually would be their daughter, Méi.

"We went to a fertility doctor, we were going to make embryos. This was after Olivia had a double mastectomy, but before her hysterectomy and ovariectomy. We were going to make embryos for what eventually became our daughter this fall," he explained.

Mulaney, who also shares a 3-year-old son, Malcolm, with Munn, said he and his wife were standing in the doctor's office when this laugh-out-loud conversation went down.

"'The great news is nine eggs survived the thaw,'" he recalled the doctor telling them. "Olivia: 'So now, we uh, combine it with his, uh, c-m?'"

At the time, Mulaney said he corrected Munn, saying, "Baby, baby. It's semen," while the doctor stated: "Guys, it's sperm."

The couple would go on to welcome their daughter in September via surrogate, following the actress' cancer journey -- a profound experience for Munn who said she "struggled" with not being able to carry their baby girl herself.

"I had so many profound emotions about not being able to carry my daughter. When I first met our gestational surrogate we spoke mother to mother. She showed me so much grace and understanding, I knew I had found a real-life angel," Munn wrote at the time while announcing the news of Méi's birth. "Words cannot express my gratitude that she kept our baby safe for 9 months and made our dreams come true."

She continued, "I am so proud of my little plum, my little dragon for making the journey to be with us. My heart has exploded."

Munn revealed she had diagnosed with breast cancer in March 2024, and was open about the procedures she underwent following her diagnosis as she battled the disease.

"We were in the hospital for Olivia's third surgery in September 2023 and she had lost a lot of blood during her second surgery, so we were both a little nervous. She said to me, 'I just read this book about Jackie O. Jackie O. never got over her husband being killed.' I said, 'No, I get it, it was a big deal,'' Mulaney recalled while discussing his wife's journey at the Instyle Imageamker Awards where he her with the "Woman of Impact" Award. "She said, 'She always regretted that she didn't move past it.' She said, 'I'm scared, but I'm taking all of this and I'm not going to let it hang over our lives. I'm moving past it.' [...] I thought how lucky our kids are to have you as their mother, how lucky I am to have you as my partner in life."

"We learned a lot from it," he shared. "We learned she would need five surgeries. We learned there was a risk of lymphedema. We learned that if we had not caught it when we caught it, things could have been a lot worse. I also learned it's not pronounced 'masectomy,' it's pronounced 'mastectomy.' It has a T in it. It shouldn't. It should be 'masectomy.' It's ironic that the word itself has a part that should be removed, I think."

Mulaney praised Munn in that moment an in speeches since for sharing her cancer story with the world, telling the InStyle crowd at the time that because Munn shared her story "there was a 4,000 percent increase in women visiting the breast cancer risk assessment. That was the first week. Olivia saving lives by speaking her truth is not surprising to me."

"She shared her story to help anyone she could," he added.