fly on the wall


An unseen observer or listener, as in I wish I could be a fly on the wall when she tells him she's pregnant. [Mid-1900s]

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.

Examples from the Web for fly on the wall