The "explanations for the hard of thinking" are common in any historical, esoteric, or sci-fi fiction scenario.
As in the immortal exchange in "The Great Muppet Caper", as Diana Rigg's character explains the entire backstory of her family's wealth and her ne'er do well brother to Miss Piggy, who she's just met for the first time.
Piggy (Puzzled) - "Why are you telling me all this"
Diana (Offhandedly) - "It's plot exposition, it has to go SOMEWHERE"