A bit later I turned around to see the farmer running up to me again. I spoke to him multiple times but all he ever said was "yes". From that point on it became painfully obvious I had a stalker, and he even followed me all the way to my Red Rocket base and the Sanctuary settlement.
So I thought I'd make some use of him, and since he had no conversation topics I ended up trying to pickpocket a gun onto him so he could help me out - it failed, he went hostile and began punching me, but Dogmeat killed him pretty quick. I looted his corpse to find a fusion core.
I reloaded the save, killed him again without doing any pickpocketing, this time he had no fusion core. Once more I reloaded, failed to pickpock a cheap item onto him, killed him, and he had a fusion core on his corpse again.
So we have two weird things going on:
- Why is this farmer following me?
- Why does making him hostile through pickpocket spawn a fusion core on him?
I did a bit of Googling around and it looks like it's a fairly common thing to have random NPCs following you, presumably because they become trapped in the "thank you" script that never ends. As for the fusion core, I can't find any prior mention of it - though I'm sure someone's now going to try this with every killable generic NPC just to see whether this can be exploited for easy and endless supplies of cores.
Has anyone experienced either of these? And in the case of the farmer, is there any way to permanently get rid of glitches NPCs like him besides murdering them? Sure, if you run away quick enough you'll leave him behind and he stops following until you get within a certain range but as soon as you are close enough he's right there running after you everywhere again.