É isso mesmo: "Caiu a ficha!"
Meaning: A belated realization of something after a period of confusion or misunderstanding.
Origin: The Oxford English Dictionary states that this phrase originated by way of allusion to the mechanism of penny-in-the-slot machines.
"I sat and thought for a moment and then the penny dropped."
The Penny drops on retailers: Hard discount types from Germany plan a UK invasion.
The penny drops for house sellers – along with asking prices
Are there any classic critical incidents which stand out for most trainees, ie, when the penny drops and behaviour changes?
It is only a matter of time before the penny drops and O2 is sued into the millions for damage to people’s health.
When the penny drops it w ill be too late.