The mirror effects were very cool.
All the tricks they used to make a character appear on one side but not the other, in fact considering the sheer amount of mirrors used, and the fact that the plot relied so heavily on them, it's impressive that we never got an accidental shot of a camera at any point in the film.
It must have been a logistical nightmare to shoot that film.
"Mr. Treehorn treats objects like women, man."