fly on the wall

Idioms and Phrases

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]

Example Sentences

Since 1984, Newsweek has made a cottage industry out of its fly-on-the-wall post-election coverage of presidential campaigns.

From The Daily Beast

He could play the fly-on-the-wall in Louis the Goon's life as long as he wanted.

From Project Gutenberg