Since Christmas, we've been amused because Humuhumu will randomly sing them whenever the fancy strikes her, no matter if Christmas is still 10 months away. (As were the elderly couple who were exiting Powis Castle at the same time as us last weekend. They applauded her, which caused her to be overcome with shyness and hide behind Daddy's legs.)
I found it intriguing that the lyrics differ from the ones I sang as a child in the US and are specifically British-English because of the use of the word "motorway". Now I'm wondering if there are other regional variations!
As a child, I mostly sang these alternate Batman-based lyrics to the Christmas carol
I sang these alternate Batman-based lyrics instead: