Hans Delbruck, the former owner of the brain Igor's supposed to retrieve, was a real person, a professor at the University of Berlin who died in 1929. His son Max went on to win the Nobel Prize for Medicine or Physiology. (Source.)

There's a gag early in the movie that you might not catch if you don't speak German. On the train, Frederick listens in as an old couple has an argument. On the train to Transylvania, the same couple has the exact same argument, but in German. (Source.)

Cloris Leachman claimed that Brooks told her that the word "blücher" means "glue" in German, which explains why the horses whinny in fear at the mention of her name. Not true; Blucher's just a common German surname. She's just meant to be a scary lady. (Source.)

Gene Hackman's line when he runs after the monster—"I was gonna make espresso!"—was totally ad-libbed. The reason the screen fades to black immediately after the line is that the camera grew was laughing hysterically and had to cut right there. (Source.)

In honor of the 40th anniversary of Young Frankenstein, Mel got a boulevard named after him in Hollywood. His comment? "People are going to walk all over me!" (Source.)

If you hadn't heard of Mel Brooks before, you probably know his son Max's stuff. Max apparently inherited some of Dad and Mom's (Anne Bancroft) talents. He wrote The Zombie Survival Guide and World War Z. Inspired by Young Frankenstein, maybe? (Source.)