"This is the longest 9 months of my life," he wrote, adding, "[Can't wait] 4 [fatherhood]." He included a photo from a Full House scene where Uncle Jesse is wearing a t-shirt that read "Bun in the Oven" as he attempts a pregnancy look.
The 54-year-old Stamos announced he is finally becoming a dad in December, when he and then-fiancee Caitlin McHugh broke the news to PEOPLE Magazine. The 32-year-old McHugh posted the first public photo of her baby bump on Instagram in January. The couple got married in Beverly Hills on Feb. 3.
"I'll be a fun dad. I've been practicing for a long time," Stamos told PEOPLE, referring to his TV roles. "I've done every schtick you can do with a baby on TV … all the bits and jokes and diaper gags. I'll probably just do all that stuff."
Stamos said they were not engaged when they learned McHugh was pregnant. Stamos said he wanted to marry her anyway, and her parents stated he "better."
"The [pregnancy] happened. Then I said, I better have a ring on her finger because it's the right thing to do, and I wanted to marry her anyway," Stamos recalled. "So I called her parents to ask, and it was like, 'You better!'"
"The look on John's face when I told him we were pregnant was priceless," McHugh told PEOPLE. "It was the look of a man who has wanted a family of his own, but wasn't sure it was going to happen for him. Now it is!"
Lori Loughlin, who co-starred in Full House with Stamos as Rebecca, Uncle Jesse's wife, is also sure Stamos will be a great father.
"I don't think John needs any parental advice. I think John is going to be a great dad but of course he knows I'm here for him should he need any but I think him and Caitlin have it covered," Loughlin told E! News. "I will say this. He is very complimentary to me about my own girls. I have two girls who are 18 and 19 and he just adores them."
Stamos returned to Uncle Jesse for Netflix's revival Fuller House, which has also featured Loughlin. The actor is working on a new series, You. According to Deadline, Stamos will have a recurring role in the Greg Berlanti-produced Lifetime series, which stars Penn Badgley and Elizabeth Lail. The series is based on the Caroline Kepnes novel about the love between a bookstore manager and an aspiring writer.
Stamos is also working on an untitled project with producers Craig Zadan and Neil Meron that will be based on his early professional life. The project is set up at Amazon.
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