In 3 BBY, during the early rebellion against the Galactic Empire various droids were freed from a scrap pile on a planetoid. At the suggestion of Chopper, the C1-series astromech droid who had freed them, the droids formed a group to help other droids in danger. This group wished for Chopper to lead them, but respected his decision to stay with the Spectres.
The group was made up of several droids of various types, including protocol droids, astromech droids, and at least one B2-series super battle droid.