Here's a tip for NPCs - give them a spirit animal.
When people talk to that NPC, just act like whatever comes into your head when you think of that animal.
Like if it's a Fox be all shifty and cunning or if it's a Finch be all twee an jumpy.
Luckily Wikipedia has a list of well-known animals, which I whittled down to a d400 through what your boss calls "sense checking", and thus here is a mighty table to work out what your NPCs act like and that.
To roll a d400, roll a d4 and a d100. But you could have worked that out yourself.
Oh, you wanted it automated? I slammed it into Logan's generator.
Roll that shit.
