John Mulaney celebrated his 40th birthday on tour with Olivia Munn and their 9-month-old baby Malcolm. 

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"Malcolm surprised John on stage last night to sing HBD with the full audience," Olivia shared on Aug. 27.

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John also uploaded a photo of himself carrying his 9-month-old baby on a balloon-decorated platform.

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"There is no better way to celebrate 40," said the shot's caption.

Saturday Night Live veteran uploaded more photos from the night, including a selfie with Olivia, 42.

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"Turning 40 with my family and a fistful of frosting," wrote Malcolm.

The pair welcomed their first kid in November 2021, after John's divorce from Anna Marie Tendler.

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"Meet Malcolm Hip Mulaney," John posted on Christmas Eve with their first photo. "He has a long future.

Seltzer is new to him. I'm madly in love with him.

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Since then, the comedian and actress have shared images and updates about their baby.

John said Malcolm is a natural traveller and could accompany him on tour this summer.

"Malcolm's a wonderful roadie," he said on June 22. Malcolm likes touring—he adored Saratoga Springs.