Along the lines of your post, old movies in general used dark fluids to depict blood, because they showed up better on black and white film than red fluids.
Buddy Epson, who eventually starred in "The Beverly Hillbillies", was the actor originally cast as the Tin Man in the Wizard of Oz. But he had an allergic reaction to the makeup and had to quit. I have seen footage of him singing and dancing "If I only had a heart". Of course, it all had to be re-shot after Jack Haley came on board to take over the role.
And for a different kind of trivia: my mother-in-law said that her mother (or maybe it was a different older relative of hers, I am not sure) would sometimes burst out laughing in a movie theater at the most inappropriate times. It was the silent movie era, and this woman could read lips. Often what the actors were really saying to each other had nothing at all to do with the actual storyline!
There was a charades TV show filmed in my hometown called Party Game and the regular threesome took on 3 guest stars each week. One of the guests (Marty Brill) asked a question of everyone on the set this particular episode that seemed simple enough to answer but wasn't. He asked "What was the name of the little girl in The Wizard of Oz. As one, everybody replied "Dorothy!" but Brill then asked "Dorothy What ?
That was decades ago and was the starting point for my love of trivia. I soon learned you didn't know movie trivia unless you knew the names of the actors aboard the crashed plane in Lost Horizon (1937)...
