The first Furby, the 2005 Furby, the 2012 Furby, and the Furby Connect, the furby of each generation, is a personal delusion that they are different creatures belonging to the same family in terms of animals.
Considering that there are two places, Furby Land and Furby Island, it is not an evolutionary system or pre-evolutionary feeling, but a theory that they may be close kinds of friends such as cats and lions, dogs and wolves.