If you use Shadow Movement to sneak into houses and a pegasus team to pull the flying sleigh... yes, in this world, it's possible to become Santa Claus! But... the Christmas tradition doesn't even exist in this world. When Rimuru tries to explain it in detail to the people of Tempest, they end up summarizing it as a "party." The Christmas cake and presents are ready, and most importantly, Kaijin and the other Dwarves create gorgeous decorations that bring the Christmas mood to Tempest. On top of that, Eren and the children treat everyone in town with their heavenly singing.
I did go to just about all 
of my friends' weddings.
تحدّثتُ فقط عن ما كنتُ أراه في حفلات زفاف أصدقائي
Ich war schließlich auf fast allen
Hochzeiten meiner Freunde damals.
Porque asistí a las bodas
de casi todos mis amigos.
Porque asistí a las bodas
de casi todos mis amigos.
C’est celui qu’on m’a servi
aux noces de tous mes amis.
Con tutte le volte che l'ho mangiato
ai matrimoni dei miei amici...
Eu conheço bem porque fui ao casamento
de praticamente todos os meus amigos.
Ну да, я ж почти у всех друзей
на свадьбах побывал…