A sudden appearance of a growling dog changes the atmosphere of a story. Just as the dog’s hackles rise, so do the reader’s. As the character slowly backs up, the reader does as well.
On the other hand, when a cute, fluffy, tail-wagging dog jumps up on the couch, the readers want to reach out and give it a good petting.
The same is true when a cat enters the room. Cats have a reputation for being aloof and a bit touchy. Whereas one cat might tolerate a scratch under the chin, others will immediately reach out with claws extended.
Your task is to write a story in which an animal appears, changing the trajectory of the story.
Have fun with this one.