fly on the wall

Noun

 * 1)  A quiet, non-participating, or unseen observer; an eavesdropper or witness.

Translations

 * Danish: flue på væggen
 * Finnish: kärpänen katossa
 * French: little mouse
 * German: little mouse
 * Norwegian:
 * Bokmål: flue på veggen
 * Nynorsk: fluge på veggen
 * Spanish: agujero en la pared hole in the wall
 * Swedish: fluga på väggen