Meet Leo Grey McElhenney!

"It's Always Sunny in Philadelphia" stars Kaitlin Olson and Rob McElhenney welcomed their second child last week -- and he's already got his very first TwitPic.

"Leo Grey McElhenney..born April 5th after 23 very very long hours. We're in love," Olson tweeted Monday night, four days after she gave birth at the couple's home. She also posted a photo of the newborn baby boy, who was sleeping when the shot was taken.

Leo is the couple's second kid -- Kaitlin gave birth to son Axel Lee September 2010.

Check out more cute celebrity kids in the gallery above!

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