I remember reading the story about how they went through different designs for the original Enterprise when Star Trek was first being produced, and eventually arrived at designs that went with the basic main section and three other sections (which became the secondary hull and the warp nacelles). As I've read it, from several sources, once the Enterprise model was completed, it was put on display, hanging on cables, for studio and network executives who would be at special event, to see what it would look like.
As the story goes (and I'm sure every Trek fan knows), the person asked to hang the model from cables hung it upside down. Everyone liked it, so they decided to just go with what they had and ended up with a spaceship that was upside down from what was originally intended.
Was this the only model for Trek that went through this "inversion?" Or were there other models they were working with early in the series that this also happened to?