Penny sings "Soft Kitty, Warm Kitty" to Sheldon in a few episodes of "The Big Bang Theory". In at least one other episode, Sheldon's mom sings "Soft Kitty, Warm Kitty" to him but with a slightly different melody. Here is Penny's version, and here is Sheldon's mom's version. Were the differences a choice of the actors, the writers, or the director, and was it done for a specific reason (possibly to show how the two women "mother" Sheldon a little differently)?

To be musically specific, Penny sings the first 3 notes as separated by a minor third, and the next 3 notes as separated by a major third. Sheldon's mom (Mary Cooper) sings the first 3 notes separated by an octave, and the next 3 notes separated by a minor 7th. The same thing repeats in the second verse for each of them.

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    While not absolutely necessary, could you provide audio samples so those of us not familiar with music terminology can hear what you're talking about?
    – MattD
    Jan 16, 2015 at 21:47
  • Good suggestion. Added. Jan 16, 2015 at 22:35
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    Not that I have the complete answer as to the why they are singing it different, but this might indicate to you which one is actually singing it wrong (or maybe they both are). I found this song sheet online here on page 21. You can see that the lyrics are arranged somewhat different, though it is the same song. It seems to me that Penny is actually singing it correctly, except for the last two measures. Maybe you can tell us: !enter image description here Jan 17, 2015 at 2:00
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    Here's a compilation of many (all?) occurrences of the song in the show: youtube.com/watch?v=fi2-U7qfMeA. The first clip is Sheldon teaching Penny the song.
    – Barmar
    Feb 2, 2018 at 1:40
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    And last night's "Young Sheldon" showed younger Sheldon's mom singing it to him. Have you compared Zoe Perry's rendition with Laurie Metcalf's?
    – Barmar
    Feb 2, 2018 at 21:51

2 Answers 2


The first time Sheldon asks Penny to sing the song, she does not know it, so he teaches it to her. He is sick and sings it a little off. So she sings it the way she remembers Sheldon teaching it to her.


I feel that, as Sheldon is so accurate about everything, this must be a mistake in the continuity...surely he would have taught Penny exactly the same tune as was sung to him by his mother?

  • Does Sheldon actually sing it the same as his mother? Check the compilation link I posted in the comments above.
    – Barmar
    Feb 2, 2018 at 1:41

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