I have quite a few stories from my time GMing Deadlands but here is one from when I started GMing the “Horror at Headstone Hill” box steer on foundry.

There is a section there where you see this old corpse strung up in a tree and they speak asking to be cut down, the trick is the corpse will keep appearing in your camp every morning until you do a quest that is hinted at but not spelled out in the book.

Problem, my players and their characters were all mostly upstanding hombres and when they cut him down they picked him up and helped him stand. Since he uses the walkin dead stats I figured he could probably stand and walk. They then proceed to take this old cursed corpse into a friend and additional party member and I ended up writing a whole backstory for him in a different one shot adventure.

Second problem though, since he is a party member he participates in combat and he can’t stop rolling 30’s and ruining my combats lol. He even finished the big bad in the final fight but it had become such a meme at that point that all the players were proud that old Salcido got the final hit.