Reba McEntire plans to sing the theme song for her new sitcom. The 69-year-old singer’s ‘Happy’s Place’ sitcom has already been picked up by NBC and Reba has confirmed that she’ll be singing the show’s theme song. Speaking to PEOPLE, Reba shared: “I’ll be singing the theme song. “We’ve started working on it, and we’ll have it soon finished. “If they say it’s a go, I’ll finish it up and have it ready for when we go to series.” Reba has also confirmed that Rex Linn, her boyfriend, will be a part of the sitcom. The country music star explained: “Rex Linn, my boyfriend, is also part of the show. W…