There is a cluster of folktale types that feature this sort of thing - and these were of particular interest to my mentor Sven S. Liljeblad (1899-2000) and his mentor, Carl Wilhelm von Sydow (1878-1952). This was part of the debate that raged in the twentieth century as to whether folktales (the oral narrative novels of the folk) fell into types or should be considered as clusters of motifs. Sven attacked the subject of the Grateful Dead, publishing his doctoral work in 1927, dealing with a variety of folktales (ATU types 505-508) dealing with the dead acting as supernatural helpers.

The folktales classified as ATU 530-559 involved animals (and sometimes objects) that act as helpers. These were also of interest to my mentor and the Swedish approach as it emerged in the 1920s because there were adaptations that occurred with these seemingly very old narratives: namely, the hero earns the thanks of animals (usually three in succession); in cultures that have a core belief that animals can transform into people and people into animals, the animals typically bestow on the hero the ability to transform into these creatures, and with that secret power, he is able to overcome obstacles. When these folktales were collected in cultures that did not have the core belief in transformation along these lines, the animals gave a hair/feather/etc. to the hero, which he could rub to summon the animal for assistance. The Swedes were interested in how core beliefs of a culture affected the folk narrative as it diffused across cultural boundaries.