编写一个简短的小故事，包含以下词语："cat"、"rainy day"、"surprise"
On a rainy day, a curious cat named Mittens was wandering outside. As she trudged through puddles, she pounced on a brown paper bag. Surprised to find it filled with catnip, she happily rolled around in it until the rain stopped. From that day on, Mittens always looked forward to rainy days, hoping for another surprise.