NPCs have lives too. They're all heroes of another story, and sometimes those stories deserve to be told. The richer and more detailed your NPCs' lives are when the PCs are not around, the more convincing and sympathetic they will be when your players encounter them.

At least that's the theory.

Transcript

{the stage magically transforms into a full-on rock band performance stage}
Scooter: {singing}
Now all I want is to earn my fair salt.
But I'm caught up in this clone plan gestalt.
My life's a big mess, it's all Crynyd's fault.
Arvel my friend, your fault again.
Floyd: Good one, Scooter. Take five.
Janice: I hope this pleases our master more than my original's final dance performance.
Janice: {softly} I heard they had to scrape my DNA from a pile of rancor droppings.
Animal: We're just here to do a job, guys.
Animal: Perform, get paid, let the boss worry about the details.
Floyd: I still say he got the best code name. "Dr Teeth".
Janice: Not that he has teeth.