As a GM, voice is your most obvious method of characterising individual NPCs. It's a lot harder to show off visual features or mannerisms. Although you can try if you really feel inspired. Masks? Expansive arm gestures while speaking? You know - these could actually work!

Just be careful not to knock over the bottles of drink on the table.

Transcript

[SFX]: shhh-woop! {bridge door opens and Link Hogthrob enters}
Link Hogthrob: Oi! You lot! Turn this ship around! Oink!
Luke: Who are you?
Link Hogthrob: Oink! Link Hogthrob.
R2-D2: That tells us precisely nothing.
Link Hogthrob: It's a code name, innit? Oink!
C-3PO: That's the third time he's said "oink". That's obviously the clue.
R2-D2: Do we have to identify the clone of every random NPC we've ever met based on their verbal tics?
GM: Yes, it's called roleplaying.
{beat}
C-3PO: Jabba's porcine henchman.
GM: Yep.
R2-D2: Showoff.