Bucky Barnes’ Vibranium Arm Looks Much Weaker After Event at Marvel Studios Guardians of the Galaxy Vol. 3Karen Gillan reprises her role as Nebula in James Gunn’s final MCU project, officially joining the Guardians of the Galaxy Vol. 1 as they set out to save Rocket and defeat Advanced Evolution. During her MCU career, Nebula has gone through some dramatic changes, both emotionally and physically. The latest of these, along with some cosmetic changes to make the Nebula look more human, comes in the form of a new prosthetic limb, adapted with nanotechnology to make the perfect multipurpose tool.