"the penny dropped" informal chiefly Brit. used to indicate that someone has finally realized or understood something.
credits
from For Some Reasons I Want To Talk,
track released December 12, 2011
Music : Arthur DE ROHAN-CHABOT, Frédéric DEMAISON, Hugo COSNARD, Jonathan DUPRIEZ.
Sparkling synthpop with an emphasis on high-wattage chords and the kind of melodies that burrow themselves deep in the brain. Bandcamp New & Notable Dec 1, 2023