Every town in the game has multiple townsfolk to interact with, starting from the Hidden Village itself, as soon as you get Gig. These NPCs change often, usually in all towns with every significant plot point or when a new place is unlocked.
Some of these NPCs appear multiple times in different places, having their own little adventures for the player to follow, but more than just talking, there are other ways to interact with them with the use of Gig Edicts.

1 - Fighting
Fighting is done using the fight edicts, such as Fight, Assault, Duel, Violate. The reward for winning the fight is GP, also allowing the unit to be kidnapped and added to your party.

2 - Kidnapping
Kidnapping is done with kidnap edicts, such as Kidnap, Betray, Bribe, Headhunt. A townsfolk must first be beaten in a fight before it can be kidnapped, it should also be noted that kidnapped townsfolk leaves your party once you start a new cycle. This allows you to get units of certain classes that would only be unlocked later in the game.

3 - Kicking
Kicking is done with kick edicts suck as Boot, Punt, Flail. It makes the townsfolk hold a grudge against you, which means an enemy unit can spawn during a story map to kill you.

4 - Merging
Merging is done with merge edicts, such as Transform, Combine, Fuse. You fight the townsfolk, and if the battle is won, one of the Hero's stats is permanently increased by a certain amount.

5 - Stealing
Stealing is done with steal edicts, such as Steal, Sneaky Steal, Amazing Steal. If the steal is successful, you get one item from the NPC; if the steal fails, you pay 10x the item's selling price. You can try again as many times as you want, but beware that you can go into debt (negative GP). Some unique decors that are usually a room's main decors can be obtained by stealing, most notably Revelation, Death Fist and Cat Paw.

Firstly, it should be noted that you can only gain the GP from fighting, merge and steal from each townsfolk once per cycle.
Some NPCs appear multiple times, such as the Sepp Historian, with different rewards, meaning you can only get one of those per cycle.

The following spreadsheet contains all the townsfolk in the game with their respective class and level, GP reward, merge stats and stolen item.
The database is divided by location and has divisors to indicate after which event (fight or event) each change happens.
Some townsfolk appear with different names, or in group, as such the NPC Number is an identification number, given in order of appearance, that is used to track the townsfolk who appear multiple times. Basically, for all entries that share the same NPC Number, you can only steal, fight and merge once with any of them, during that cycle.

The spreadsheet:

https://docs.google.com/spreadsheets/d/1yRA0T1yXmEt89eKOx2GoKSu8OzC0BJJjSvnGGCAtFdY/edit?usp=sharing