The Dragon Sheep Chronicles are two short videos released alongside the How to Train Your Dragon: The Hidden World Blu-Ray disc, and as an iTunes extra that comes with buying the HD version of the film. Each film involves the sheep from Berk.
Friend vs Food
This video featured Hiccup's various attempts at stopping the dragons from eating the sheep and how they came to have their dragon costumes.
The Secret Sheep Society
This video featured a sheep called Margaret and its attempts at leaving the island of New Berk.