A Robot Buddy who happens to be made out of light. Holography is the very real technique of using lasers to create a three dimensional image. It's very difficult and requires precisely calculated conditions and a bunch of costly hardware, but it's visually stunning, at least the first few times you see one. Technically, what is popularly called a "hologram" in science fiction is really called a volumetric display, as a true hologram is recorded onto a visual medium that provides the illusion of volume. The character may be constrained by power or the availability of a projector to add flavor.