Busy Philipps Wishes Her Child Birdie a Happy 13th Birthday: 'Perfect in Their Uniqueness'

Busy Philipps/Instagram

Busy Philipps is officially the mother of a teenager.

The Girls5eva actress, 42, celebrated her older child Birdie Leigh's 13th birthday on Friday, posting a series of throwback photos with a sweet tribute. "Before I had kids, I dreamed of a baby I would instantly recognize, the child of my dreams (btw, it was a baby that looked like me)," she started in the caption.

"But can I tell you something? I was VERY surprised when I gave birth to Birdie and saw them for the first time," Philipps wrote. "They weren't what I expected. At all. Honestly, I didn't know who they were. But they were exactly perfect in their uniqueness. Truly. Everyone saw it instantly. And I did too even though I would whisper, 'who are you?' To Birdie at 3 am while I was breastfeeding."

RELATED: Busy Philipps' Child Birdie Lands Non-Binary Acting Role on Amazon's With Love: 'Made Me Cry'

"The greatest news any parent could ever receive is that, if you do it all pretty well, your kids will tell you who they are when they're ready. Birdie Silverstein is officially now the teenager I was always waiting to hang out with; but they are also the kid I adored and fretted over and didn't know what exactly to do with at times and also, the baby so perfect that I never ever dreamed of them because my imagination just simply was too damn small. Happy 13 on the 13th Birdie Leigh Silverstein. You're the best best best. And I love you more than anything," she continued.

Philipps previously posted a throwback photo of her 2008 guest role on Terminator: The Sarah Connor Chronicles, during which she was pregnant with Birdie. "13 years ago, my friend Josh was like, 'want to be on a few episodes of my tv show pregnant?'" she recounted. "And I was like, 'how pregnant never mind I'm broke yes thank you so much except I'm due in August so it'll be before then?' And he was like, 'yes!'"

"And then, in August, the week before I gave birth to my first kid- there I was, on the set of Terminator: The Sarah Connor Chronicles for Fox," she continued. "Am I the MOST pregnant person to ever be on a tv show in a guest starring role? I literally have no idea. But you can look at this picture and decide for yourself. OH. Also, there was a guy who worked as an AD trainee on that show and when Birdie got the job on With Love, he was there as the 2nd AD!! What are the chances?! Also. Birdie was almost 10 pounds but yes, I gained many more than that. Please wait for the pics of my Bird…."

Philipps also showed off the yurt she had setup in their backyard for a birthday slumber party, which included a popcorn machine and a giant outdoor screen to watch Young Royals. "We got all the kids tested, we got tested," she noted in the clip. The gathering also featured three cakes: a funfetti sour cake inspired by Olivia Rodrigo, a red velvet option inspired by Taylor Swift, and a dark chocolate Young Royals cake.

The Freaks and Geeks alum shares Birdie with husband Marc Silverstein, 50, whom she married in 2007. They also share 8-year-old daughter Cricket Pearl.

Philipps revealed in December that Birdie came out as gay at 10 years old, and that they prefer they/them pronouns, which she admitted she still has trouble remembering. "So Birdie, my out kid, prefers they/them," she said on her Busy Philipps Is Doing Her Best podcast. "I f— up sometimes, but I'm trying my best at that, too."

RELATED VIDEO: Busy Philipps Answers Your Most Candid Mom Questions

Birdie landed a recurring role as a nonbinary character on the upcoming Gloria Calderón Kellett Amazon Prime Video romantic comedy With Love.

"I first met Birdie when they were a baby. It is thrilling that I now get to have them on my little show," Calderón Kellett wrote on Twitter, as Philipps quote tweeted: "This just made me cry."