I’d completely forgotten about this, but Shakespeare’s most famous stage direction was “exit, pursued by a bear.” It’s from uhhhh, midsummer night’s dream? Not 100% sure on that.
I just found a great one - the author used hydrocephalus (water on the brain) when they meant hydrophobia (rabies). Being chased by a monster that is like a dog with hydrocephalus might be scary, but probably not in the way the author intended.
Story time: when we were much younger, my sis and I shared a townhouse. She was working as a vet tech at the time and so she was always bringing home critters over weekends or vacations that needed extra attention, and one time it was a puppy with hydrocephalus that had a drain in. Really little one, its eyes weren't even open yet. So she comes home and hands it to me while she sets up its bed and all, and just as she's telling me how she's worried because it hasn't pooped all day, the little sucker poops all over me. Of course you can't get mad, so we laughed and sure enough, all weekend, whenever I picked it up, it pooped. Apparently that's my superpower. (puppy turned out fine eventually, so happy ending)