Long ago, before color moviemaking became commonplace, before f-bombs replaced the incensed g-d exclamations, before bloopers made their way to television shows and special features, there was the "Breakdown." The what? In 1936, a Breakdown was "when one or more people get 'tetched in the head' at a most opportune time -- causing the director, the assistant director, the unit manager, the producer, etc., to lose their mental balance and their digestive organs fail to function."
I just learned this today through a killer movie
That's what gets me. Although older films can sometimes seem like they're from another world with the actor's delivery and poise, when they slip out of character, they're not that much different from the modern us at all -- save for their sassy suits and slightly retro accents. It's too bad we didn't get the chance to see that natural side a little more often.