"Merely corroborative detail, intended to give artistic verisimilitude to an otherwise bald and unconvincing narrative."An element is included in a work, just because the element makes the story better in some way simply for having it, similar to adding spices and seasonings to food. These elements don't drive the plot or have a narrative purpose, and aren't genre staples. They can add to characterization or World Building, but mostly the point of them is that having these elements is so much better than not having these elements. Now even if these elements have some importance to the story, it's similar to a MacGuffin in that the form needn't be any of the elements, but it's still better to have them.
— Pooh-Bah, The Mikado
A Super Trope to
These animals are so much better than without these animals. Or, depending on the animal, much worse (adds danger and suspense).