The hamster was an entity that had its own designated cage. In 0 BBY, the stepbrothers Phineas Flynn and Ferb Fletcher made a hamster cage for a small group of womp rats.
Hamsters are a reference to a real-world animal with the same name. The 1984 television movie Caravan of Courage: An Ewok Adventure used many real-world animals to portray different species. This included a hamster, although its species has yet to recieve an in-universe name.