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.
Sneaking into a... girl's? ...bedroom 
and standing next to her bed
التسلّل إلى غرفة نوم... فتاة؟ والوقوف بجانب سريرها
aber sich ins Zimmer eines Mädchens
zu stehlen und auf ihr Bett zu steigen …
pero entrar en la habitación
de una chica de noche
pero entrar en la habitación
de una chica de noche
s’infiltrer dans la chambre d’une gamine
jusqu’à son lit,
ragazza
mas entrar no quarto de uma garota que está
dormindo e ficar ao lado do travesseiro dela...
Но всё же… к девочке?..
кажется, впервые в спальню пробираюсь…