Last year, Big Bang Theory was shut down going into its eighth season, and production was delayed as the cast dug their heels in and refused to go back to work until they were granted a pay raise.

That drama was resolved, but Big Bang‘s producers, and its network CBS, now find themselves facing a lawsuit over the ownership of the popular ‘Soft Kitty‘ song, which is a recurring element of the show.

An early episode of the series features Kaley Cuoco‘s Penny serenading Jim Parsons‘ Sheldon with a lullaby called ‘Soft Kitty’ – you can see a clip below should you desire to experience it.

The song has been used in numerous episodes of the show since, elements of it have been featured in official merchandising, and it has even been performed at Comic Con events.

The lawsuit over the song comes from the estate of deceased New England schoolteacher Edith Newlin, who wrote a poem about a ‘Warm Kitty’ in the late 1930s, that was later turned into a song.

Newlin’s daughters claim that Big Bang has a version of their mother’s song – with the lyrics slightly changed – for years, and made it a key part of their promotion, without offering any credit or compensation.

In 1937, a group called Willis Music Co published a book called Songs For The Nursery School that featured the sheet music for ‘Warm Kitty’, credited to Newlin, as an adapted English folk tune.

The current owner of Willis Music has commented, saying that Warner Bros approached them to use the song, with slightly altered lyrics, and that the appropriate permissions were granted.

This fact is not in dispute, however, Newlin’s family claim that they themselves were not approached about the use of the ‘Warm Kitty’, and are now suing the show’s producers for unspecified damages.

The specifics of Edith Newlin’s contract with Willis Music are not yet clear, but will be important if the case is to go ahead. Big Bang Theory‘s producers and the CBS network have yet to comment.

Story: NY Times