I thought it would be a really neat motif for the Gems, and their constituent diamonds, to be based off of animals. They all have a different set of behaviors based off of the animal that they are modeled after, and for Spinel, what is more appropriate than that of a primate? And more specifically, a Long-Tailed Macaque? Known for their intelligence, curiosity, cautious temperament, and volatile and even aggressive behavioral patterns, this seemed a suitable species for Spinel to fit into.

Given the propensity for this species to bear the patterns of behaviors above, since Pink left, her moods have been a bit more unstable, but she still bears the deeply buried playfulness that is a staple of many primate species, existing as a nod to her initial purpose as a playmate, or more aptly, a source of entertainment.