One of mine is the 3D hologram of yourself flipped upside down, when staring into a curved shaving/vanity mirror at the wrong focal point (i.e. further away tha

One of mine is the 3D hologram of yourself flipped upside down, when staring into a curved shaving/vanity mirror at the wrong focal point (i.e. further away than normal). Your eyes receive two images due to focal pont being earlier than expected, and you can resolve them into an (upside down) 3D hologram of yourself! At first I thought I stumbled onto some clever new hologram tech, though it quickly del apart once I realised that the source image has to already be 3D, and if you can generate an actual 3D image at the source, then you don't really need a mirror to see them...