On Wednesday the Jobs actor shared a photo of his living room on the show filled with large stuffed animals, toys and miniature cars as part of his character Walden Schmidt's adoption storyline.
The sitcom currently follows Walden and Jon Cryer's character Alan Harper as they prepare to adopt a child together.
"Nesting.... Too much?" 36-year-old Ashton captioned the image, which some fans initally thought was a look inside his and Mila's home.
Meanwhile the Iowa-born star's fiancée is in the last stages of her pregnancy.
Black Swan actress Mila has been seen out and about displaying her prominent bump as she gets the last few essentials before her baby arrives.
Mila and Ashton are getting ready to become parents for the first time
Like Walden and Alan, Mila and Ashton are have kitted their home out with a new nursery.
The nursery is decorated green with baby animals," a source told Radar Online. "It's jungle-themed."
Mila described Ashton as 'the love of my life'
Ukraine-born Mila recently opened up on how getting engaged and expecting a baby were a far cry from plans she made when she was younger.
"I never wanted to get married," she said. "From the age of 12, I prepared my parents for no marriage."
Her feelings changed, however: "I found the love of my life," she said. "Now my theory on weddings is: Don't invite anyone. Do it privately and secretly. My parents are okay with that. They're just excited that I said yes."