King of Hearts was a European 1967 film. Made during the
Vietnam war, it's seen as an antiwar piece, but of course the film doesn't touch on that. Instead, it takes place during
World War I.
Simply put, the German army is retreating from a certain French town, but they rig it to detonate on a timer once the Allies arrive to take control. The French evacuate the town, and someone notifies the Allies. The Scottish army sends one French-speaking man in alone to infiltrate the city and disarm the explosives before the troops arrive.
Unbeknownst to the soldier, the Germans accidentally leave the town's Insane Asylum unlocked, and the delusional people all pour out into the town, moving in and dressing up and acting as the local village folk (bishop, hookers, general, barber, duke, etc.). The soldier doesn't immediately know this, so he wanders the town asking the people for information and getting only absurd answers back. By the time he catches on, the townsfolk (all insane) want to crown him their king. Meanwhile, he has to elude the Germans and save the oblivious people from the time bomb.
The movie has some charm. Although it was a big hit in the 1960's and 70's, the college students today don't seem to like it. The film has English and French and even some German dialogue, with subtitles.