Call it a copout answer, but since OP didn’t specify it has to be real:
12-400mm f/2 fisheye macro tilt-shift with interdimensional optics that allow the whole thing to be packaged for the size of an 85mm f/1.8. Metal mount, metal filter threads, 3 stop image stabilization, and optically sharp corner to corner even wide open.
Call it a copout answer, but since OP didn’t specify it has to be real:
12-400mm f/2 fisheye macro tilt-shift with interdimensional optics that allow the whole thing to be packaged for the size of an 85mm f/1.8. Metal mount, metal filter threads, 3 stop image stabilization, and optically sharp corner to corner even wide open.