Zhang Guolao is one of the standard Eight Immortals. He is shown as an elderly man with a bamboo tube drum and is famous for riding a white donkey backward. The comic image signals an immortal who does not follow ordinary expectations.
The folding donkey
In popular stories, Zhang can travel an immense distance on his donkey. When the journey ends, he folds the animal like paper and stores it away. A splash of water restores it when needed. The detail belongs to wonder tales and artistic identification, not to a verifiable biography.
Tang records and later lore mention an eccentric recluse called Zhang Guo who was summoned to court and associated with unusual powers. It is possible that memory of a real hermit contributed to the immortal, but the evidence does not establish that every later miracle belongs to a historical person.
Age, refusal, and freedom
Zhang repeatedly avoids official service, sometimes by feigning death. His great age and his independence from rulers fit the image of a Daoist adept beyond normal ambitions. In art, the tube-shaped instrument or the backward ride can identify him even when the full group is absent.
The story is part of the same later grouping described in Eight Immortals Cross the Sea. It can also be compared with Ma Gu, another figure who measures time differently from mortals.