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.
So long as I, the one regarded as Dwargon's 
most cultured citizen, am alive...
ما دمتُ أنا، الشّخص الّذي يُعدّ المُواطن الأكثر
...ثقافة في دوارغون، على قيد الحياة
Als kultivierter Mann aus Dwargon
Por algo me llamaban 
el hombre más culto de Dwargon.
Me llamaban el hombre más culto
de Dwargon por algo.
Je suis reconnu comme étant
le plus grand savant de Dwargon,
Sai, mi chiamavano il più esperto di cultura di Dwargon.
Em Dwargon, eu sou considerado
o maior entendido em cultura,
Не зря меня называли главным ценителем!
Пока я жив — не допущу таких рассуждений!