This interesting form is created when yogis do a pose called the rabbit pose. I have been mystified as to why it is called that. Searching for an answer I eventually found this explanation from Yoga International magazine:
“Rabbit pose—alternately called hare pose, hare headstand, and sasangasana (sometimes written shashankasana)—is an asana that evokes nostalgia for childhood playfulness, a deep connection to nature, and the calm gentleness of bunnies.
In Sanskrit the moon is called sasanga, “having the marks of a hare.” If we were to look closely at the moon, perhaps we could find a rabbit-like shadow, and the curled roundness of this pose reflects both moon and rabbit in shape.”