You can make the act of saving the cat a turning point in the story. Let's say in a fantasy novel, a young hero is on a journey. Saving the cat could be the moment when they first discover their hidden power. The cat could be in a magical trap, and when the hero saves it, they unlock a new ability within themselves. This ties the act of saving the cat to the character's growth and the overall plot development.
One way is to use it as an early character - building moment. Have your protagonist save the cat right at the start of the story. This immediately shows the protagonist's good side. For example, if it's a detective novel, the detective saves a cat on the way to a crime scene. It gives the reader a positive impression of the character from the get - go.