Charlie Day, Mary Elizabeth Ellis Welcome Baby Boy 29407

Charlie Day, who stars in the sitcom "It's Always Sunny in Philadelphia," and his wife Mary Elizabeth Ellis, who recently guest-starred on the comedy "New Girl," welcomed a son, Russell Wallace Day, on December 15, reports.

"We are overjoyed and overwhelmed at the amount of love that ushered our baby into the world," Day, 35, and Ellis, 32, tell PEOPLE.

PEOPLE reports that the baby's name comes from the couple's family tree — Russell comes from Ellis's side and also honors a departed friend, while Wallace comes from Day's.

Visit Celebrity BumpWatch for more celebrity pregnancy news from