Backstory transposition been super helpful in my campaigns.

Though once in awhile my party notices when “Pops”, the bartender with a heart of gold, turns out to be the heir to the throne, and not the super obvious young orphan girl with the mysterious past. It’s not my fault the party decided they would do anything for “Pops”, and kind of disliked the orphan. I just rolled with what was working for them. Who knew Pops was royalty? Literally no one until the plot demanded it.