BB-4 is a spherical astromech droid appearing in Star Wars: The Last Jedi. It serves as a support unit associated with the Resistance, helping with technical tasks and maintenance rather than acting as a major combatant. The character is part of the broader droid tradition in Star Wars, contributing to the story’s sense of lived-in space adventure. BB-4 does not have a major individual plot role, but it helps reinforce the operational and cinematic presence of the Resistance alongside other droids and personnel.