Turns out everyone's favorite "Soft Kitty" lullaby was not The Big Bang Theory's (TBBT) original at all.

The kin of Edith Newlin, a New Hampshire teacher who published a song/poem about a "soft kitty" in 1937, has filed a complaint against CBS and other TBBT executives and writers for copyright infringement for years. The show premiered in 2007 and had the song as a running gag since Season 1, Episode 11 which aired March 2008.

According to the Associated Press, Edith Newlin's daughters, Ellen Newlin Chase and Margaret Chase Perry, declare that the show's song uses lyrics similar to those written by their mother in the 1930s without paying for the rights. Apparently, the Newlin siblings, in their 70s, have not seen any episode or season of The Big Bang Theory. It was only when Ellen did a research on her mother's history in August 2014 did she stumbled upon a blog post dissecting the lyrics of the lullaby.

The only difference between the show's version and Newlin's poem is that the words "soft" and "warm" were in different order. The lullaby's opening line is, "Soft kitty, warm kitty, little ball of fur..." while Newlin's version starts with "Warm kitty, soft kitty, little ball of fur." Entertainment site, TMZ, has posted a photo of the original Newlin lyrics page.

The lawsuit claims that Newlin has not been credited, giving the viewers the assumption that it is the show's original composition.

"The Soft Kitty lyrics are among the best-known and most popular aspects of The Big Bang Theory," the lawsuit claimed. "They have become a signature and emblematic feature of the show and a central part of the show's promotion."

CBS also sells "Soft Kitty" merchandise which includes clothing, computer accessories, mobile phone covers, wallets, air fresheners, magnets, plush toys, among other products, which should be also copyrighted and rights be paid.

Robert Pietranton, a spokesman for Warner Bros. Entertainment, which produces the show, said Tuesday the company would have no comment and would answer allegations through legal action.

Edith Newlin, who died in 2004 at age 99, had worked as a nursery school teacher in Alstead, N.H., for about 35 years, and her daughters still live nearby.

The lawsuit clarifies that Warner Bros. Entertainment and the show's producers have sought permission from Willis Music Co., a Florence, Kentucky-based company that had published the lyrics in a book, "Songs for the Nursery School". Unfortunately, Willis Music failed to consult or ask permission from the Newlins before giving TBBT executives the go signal.