Soft Kitty Warm Kitty Little Ball Of Fur Happy Kitty Sleepy Kitty Purr Purr Purr Shirt. “Warm Kitty” is a children’s song, popularized by the characters Sheldon and Penny in the American sitcom The Big Bang Theory where it is rendered as “Soft Kitty”. The lyrics on The Big Bang Theory are: “soft kitty, warm kitty, little ball of fur! Happy kitty, sleepy kitty, purr purr purr!” A scene depicting the origin of the song. The nursery rhyme about a little kitten falling asleep has become synonymous. The song ‘Soft Kitty’ first appeared in Big Bang Theory Season 1, when Penny sang it to a sick Sheldon to calm his nerves. Little ball of fur, Children’s performer Patsy Biscoe released a version of Warm Kitty on her album.