MWC 922: The Red Square Nebula. Source
The square-like appearance of this nebula is no artifact of a camera. The nebula is actually shaped like this. We are not quite sure how this nebula managed to pull of this shape, but some have hypothesized that the star imbedded in the center threw off cones of material that achieved almost perfect right angles and we are viewing these cones from the side. It seems like a good explanation to me, but who knows what's actually going on?