By Holly Lebowitz Rossi
December 19, 2011
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