Sleipnir
Son of Loki and SvaĆ°ilfari
About
Once upon a time, Loki gave birth to a horse, a beautiful, wonderful male foal with 8 legs.
The how and the why is relatively simple. The gods asked Loki for help. He helped. When circumstances outside of anyone's control went wrong, they blamed Loki and forced him to fix it on pain of death. So Loki turned into an attractive mare to distract an attractive stallion, in order to fix the gods' problem. Then Thor came in with his hammer, and Loki and Thor saved the day as per usual. As per usual Thor was given the hero treatment and Loki would have been given the short end of the stick, but he sort of disappeared for a while... a little over a year in fact.
When he returned, he had in tow a happy gangly 8 legged foal. To deflect the scorn and mockery he was bound to face from the gods for switching genders and giving birth, also the scorn for his idea going wrong, also to prevent what happened to his other 3 children from happening to this new little darling, Loki gave his child to Odin. Loki though Sleipnir would be safer under someone else's care, and he was right. To this day Sleipnir is a great and renowned hose, prized for his differences rather than outcast. Loki was happy to do right by at least one of his children.