Stop shadows from casting on object (like a hologram)

There is a shader field called "ReceiveShadow" that is used by the scrolling and additive shaders. An example can be found in the Perfect Private Aquarium. I don't know if you could exploit this in your object or not, or even if it does what you're trying to accomplish, but it may be worth taking a look at. It also appears in the Fit4Fish Crystal Fish Bowl from the base game. Maybe you could try cloning that item for your object. I would take a look at that fishbowl in the game first though, to make sure that shadows aren't cast on the water part (the part that uses the shader with this shader field).