It's not the kind of cookie you're thinking of, though. See those dark, shadowy lines on the wall behind Scotty? Those are made by using a cuculoris, or, as it's called in movie-making slang, a cookie.
In lighting for film, theatre and still photography, a cuculoris (occasionally also spelled cucoloris, kookaloris, cookaloris or cucalorus) is a device for casting shadows or silhouettes to produce patterned illumination. The word is sometimes shortened to cookie or coo-koo. The cookie is used to create a more natural look by breaking up the light from a man made source. It can be used to simulate movement by passing shadows or light coming through a leafy canopy.
Here's another shot - see the shadowy lines in the doorway in the back?
Star Trek was famous for its use of wagon wheel shaped cookies. Pay attention the next time you catch an episode!
