Buttercup is a rough and tumble terrier mix puppy who looked so much like the lasted toy sensation "Cuddle Up Buttercup", that kids thought she was the toy come to life and would always try to grab her, two such kids being Miffy and Tiffy. After meeting Lucky and Cookie, she was brought to Shelter 17, where Strudel learned that her perfect person was a girl named Izzy.
When Izzy arrived to get her, Buttercup was dismayed to see her in a ballerina outfit, and rejected her for being too "girly." She chose intead to be adopted by Percy, believing him to be an adventurous boy who liked to play cowboy. She soon learned that Percy was just rehearsing for a play, and was actually prissy and soft, making her have a tea party with his stuffed animals.
With Lucky's help, she escaped, but was then found by a reckless boy named Henry, who tried to make her cross a dangerous rope bridge. Just as she was about to fall, Izzy and her mother arrived, having been brought by Cookie. Izzy saved Buttercup, proving that she was nowhere near as girly as she looked in the process. Realizing that Izzy really was her perfect person, Buttercup choose to stay with her.