Mary Elizabeth Ellis and Charlie Day Mary Elizabeth Ellis and Charlie Day

It's Always Sunny in Philadelphia stars Charlie Day and Mary Elizabeth Ellis are expecting a baby, US Weekly reports.

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"I'm excited," Day told the magazine on Saturday. "Who wouldn't be excited about being a daddy? Well, maybe a 16-year-old in high school wouldn't be excited, but a 35-year-old man like me is looking forward to something bigger than himself."

Day, who can currently be seen on the big screen in Horrible Bosses, wed his Sunny costar in 2006. This will be the couple's first child.