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.
Come to think of it, it's almost 
Christmas in the other world, isn't it?
على ذكر الأمر، اقترب عيد الكريسمس
في العالم الآخر، أليس كذلك؟
Stimmt ja, in meiner alten Welt
wäre jetzt alsbald Weihnachten.
En mi antiguo mundo
ya debe acercarse la Navidad.
En mi antiguo mundo
ya debe acercarse la Navidad.
J’y pense… Dans mon monde d’origine,
c’est bientôt la période de Noël.
Ora che ci penso, nel mio vecchio mondo
tra poco sarà Natale.
Agora lembrei que logo vai chegar
o Natal no meu mundo antigo.
О, кстати… а ведь в моём былом мире
уже скоро Рождество?