It was portrayed as Sheldon's comforting song. The lullaby's lyrics go like this, "Soft kitty, Warm kitty, Little ball of fur ...

But as per reports, the song isn’t a creation of the show, and its origins can be traced back to a school teacher in New Hampshire, who wrote a poem titled, “Warm Kitty” in 1937 (via USA Today). But ...

In season six, Sheldon sings the same song to calm his newborn niece ... the 16-year-old actor holds his "new niece" and ...