A lawsuit has been filed against the makers of TV show The Big Bang Theory over the ownership of the song Soft kitty, reports aceshowbiz.com.
The song has become the show's character Sheldon's comfort whenever he's sick or troubled.
Late poet Edith Newlin wrote lyrics of the song Warm kitty in 1937. Her daughters, Margaret Perry and Ellen Chase, thought CBS should pay royalty.
They filed a lawsuit in a federal court in Manhattan, which said: "The Soft kitty lyrics are among the best known and most popular aspects of The Big Bang Theory. They have become a signature and emblematic feature of the show and a central part of the show's promotion."
The song used in show only changes the order of Mr Newlin's lyrics. It was first used in a 2008 episode by both Sheldon and Penny before it was repeated in seven more episodes.
The Big Bang Theory made the song so popular that CBS made a merchandise out of it, including coffee mugs, hoodies, T-shirts, toys and key chains.