10 things you didn’t know about The Big Bang Theory

3. Soft Kitty Is A Real Song

Whenever Sheldon was feeling sick when he was a child, his mother would sing him “Soft Kitty.” The song has made numerous appearances throughout the series, particularly being sung by Penny early on in the show.

Whereas the song was popularized by The Big Bang Theory, it originates from 19^th century Poland. The modern version of the 20^th century translates to “Warm Kitty” but the writers edited it to “Soft Kitty”. While the lyrics are different, the tune is the same. Executive producer Bill Prady first heard the song at his daughter’s pre-school.