It is a Christmas tradition from some regions of Spain (especially from Catalonia and Aragon) and Andorra - https://en.wikipedia.org/wiki/Ti%C3%B3_de_Nadal

It is very peculiar but related to similar traditions from other countries. It is about a wood log with a smiley face. You have to feed it so that on Christmas eve it can "poop" you some presents! To do it, you have to hit it while singing a song.

Love to explain it to my foreign friends and penpals because it is funny and unknown, so a Stamp could be fun too! Thanks for your nice work :)