Using Hero Forge I created the two full grown bull-reindeer hybrid twins.

Alvaro and Algea are now fully grown bull-reindeer hybrids. They have the size and massive muscle mass of their Taurus side.The female reindeer are deeply impressed by Alvaro's physical appearance and his enormous strength, which he uses to help Santa Claus with the preparations, like carries the huge sacks of children's wish letters, large logs of wood for the workshop, carrying piles of presents and other tasks that require muscle strength require. Beneath his massive muscle mass lies a kind, generous, intelligent, educated, cultured and noble character.
The reindeer men are a bit unsettled by Algea's physical appearance. But the more powerfully built male reindeers are fascinated by Algea and like to test their strength against her. As massive as Algea is for a female, she has a very kind nature. She is generous, listens when you have problems, is intelligent, cultured and educated and helps where she can (not just through muscle power), you feel comfortable in her presence.
What's bigger about the extraordinary twins than their huge muscles is their love for children. With their strength and other qualities, they are ready to help children when injustice happens to them and they have to suffer.
They are willing to help nice kids and make the naughty kids reconsider their wrong actions and change (not to get gifts, but simply because it's the right thing to do).