NPCs have personality too. All too often they are treated as nothing more than props for the PCs to interact with in a completely straightforward manner. But some of the characters in your world are going to be practical jokers, or people who can never take anything seriously, bunny-ears lawyers. Make sure the PCs meet some of these people.

It'll make their life more interesting, realistic, and fun.

And it's guaranteed to make your GMing job more fun too.

Transcript

Rebel Crew Chief: This R2 unit of yours seems a bit beat up. Do you want a new one?
Luke: Yes, please!
Rebel Crew Chief: Oh, sorry, I was only offering to be polite. Don't got none.
R2-D2: Can I afford a second of time to come out of calculation mode and say something?
GM: It's up to you. If you want to.
R2-D2: Ahem. Sod off, moisture foister.
[SFX]: < ni-ting ka-kibuzz ding >
C-3PO: Don't take any shortcuts, Artoo. Get those calculations right. We want everyone home safe.
Luke: Sorry for trying to get rid of you, R2.
Luke: I should have known the safest place to be is whatever ship you're on.