Wrinkles is a big gray cat owned by Sierra, who gave him his name due to his wrinkly face as a kitten. He has a distinct personality and prefers not to always sleep on Sierra's bed, which her mother attributes to his attitude. This reflects a common trait seen in many cats, suggesting that they all have unique temperaments.

In the story, Wrinkles plays a significant role in Sierra's life, representing the companionship and quirks that pets bring. His behavior and attitude contribute to the dynamics within the household, highlighting how pets can be both challenging and endearing, making them an integral part of familial relationships.