Where do they come up with this stuff?

We were able to attend Caleb's (our nephew) pre-school Christmas concert. It was so fun. I loved watching him sing & get so excited, I can't wait until Lucy can sing. One song they sang was funny or silly or insulting to fat people?
Not sure..you decide. Sang to the tune of jingle bells...

I heard a reindeer hoof, then Santa dressed in red,
Came crashing thro' the roof and landed on my bed.
I thought it was a dream, but quickly did I wake,
As soon as I heard Santa scream, "I want a piece of cake!"

[Chorus]
Oh, Santa Claus, Santa Claus, you are much too fat;
I was sleeping peacefully but not my bed is flat. Oh!
Santa Claus, Santa Claus, how much do you weigh?
I'm glad I'm not a reindeer that has to pull your sleigh!