fly on the wall

Idioms  

1. 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]

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Example Sentences

“As I said during our town hall, some of the most formative moments of my life happened in rooms where I was a fly on the wall, listening and learning,” Ellison wrote in his email.

From Los Angeles Times

Who wouldn’t love to be a fly on the wall when the extended Vance family gets together?

From Los Angeles Times

His notes show him wrestling with a decision he hadn’t let himself reckon with before: Was it time to stop being a fly on the wall and start taking action?

From Salon

Give us some fly on the wall info.

From Los Angeles Times

“But Joey is very reserved, a fly on the wall. She’s an observer. She doesn’t want to be the center of attention. She’s there to do a job and say, ‘bye.’

From Los Angeles Times