Soft Kitty

In the Season 1 episode "The Pancake Anomaly," Penny sings a song called "Soft Kitty" to Sheldon in an attempt to soothe him while he's sick. The song became a staple on the show and was sung several times throughout its run. However, it was "Soft Kitty" that caused some sticky legal problems for the series.

Warm Kitty

In 2015, Ellen Newlin Chase and Margaret Chase Perry sued CBS and its parent company Warner Brothers. The sisters accused "The Big Bang Theory" of lifting the words and music for "Soft Kitty" from their mother, Edith Newlin.

The Case

Edith Newlin, an elementary school teacher had a poem published called "Warm Kitty" in a 1937 book titled "Songs for the Nursery School" with remarkably similar phrasing. Her daughters claimed the show's producers had engaged in copyright infringement.

The Verdict

The lawsuit made its way through the legal system for two years before being dismissed in 2017. A U.S. District Judge determined that the daughters had failed to prove they owned their mother's copyright. Though the issue has long settled, it's definitely the shows most interesting and largely unheard of scandal.