Former "That '70s Star" Danny Masterson and wife Bijou Phillips pulled off the impossible: They had a baby in Hollywood without anyone knowing they were expecting!

Masterson, 37, revealed the big news on Instagram Wednesday night -- posting the first photo of the couple's adorable little girl.

"Hello friends.Beyond thrilled to announce The birth of our daughter Fianna Francis Masterson," he wrote along with the photo above. "Mom and baby are doing amazing. You can all refer to me as dj dadpants from now on."

Bijou reveals little Fianna was born on Valentine's Day, weighing in at 8 lbs, 5 oz.

"She is a perfect valentine," the new mom added.

While we're shocked they were able to keep the pregnancy a secret, photos of Bijou taken in January show she never really got that big -- so it wasn't too hard to keep undercover until now.

Congrats to the happy couple on their baby girl! See more adorable celeb TwitPics of their kids in the gallery above.

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