Olivia Munn and John Mulaney Dress Son Malcolm as His Grandmother for First Halloween: 'Identical'

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Olivia Munn/Instagram

Malcolm Hiệp is channeling one of his favorite ladies for his first Halloween.

On Monday, Olivia Munn shared a series of adorable pictures of her and John Mulaney's 11-month-old son dressed up as her mother Kimberly after teasing what they chose for the infant's first costume.

"We did it. We came up w a Halloween costume we LOVED," Munn wrote Sunday on her Instagram Story. "But now we're so tired. I'll post tomorrow. Happy Halloween!"

She revealed the hilarious finished product on Monday, prefacing the photos: "Happy Halloween!! Here is Malcolm dressed as my mom."

Malcolm was the spitting image of Granny Munn as he donned a black bob wig with a grey printed t-shirt, red floral pajama pants and seafoam flip flops, while sitting on the phone with some snacks and a phone.

RELATED: Olivia Munn Celebrates Son Malcolm Turning 11 Months, Jokes He 'Loves the Fall' Despite His Frowns

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Olivia Munn/Instagram

"Identical," Olivia wrote with a photo of her mother in almost the exact same pose with snacks in her lap and a phone in her hand.

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The X-Men: Apocalypse star also provided a checklist for completing the look: "The sunflower seeds strewn about, Wheat Thins, extra long Slim Jims, flip flops, floral pants, novelty T-shirt, always watching Vietnamese YouTube on her phone."

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Olivia Munn/Instagram

She also shared photos of Mulaney, 40, with her mother and their baby boy in costume, writing, "She's also John's best friend."

Last week, Munn celebrated her son turning 11 months old with some funny pictures of Malcolm playing outside and looking unimpressed while posing on the ground, which was filled with brown and yellow leaves.

RELATED VIDEO: New Mom Olivia Munn Laments 'Low Supply' of Breast Milk: 'Breastfeeding Is so Hard'

"11 months old today and loves the fall," Munn quipped on her Instagram Story with the first photo. In a second snap of Malcolm looking at the ground with a furrowed brow, she wrote: "Loves it."

PEOPLE previously confirmed that Munn and Mulaney welcomed their first child on Nov. 24, 2021. The pair first introduced their son to the world on Christmas Eve with photos of him sleeping inside a cozy blanket.