So there's this bug that's been showing up a lot lately. If anything with an automated 'On Death' ability(like Propeller Mutant or Jil Warka) comes into the zone(battle zone mostly, but sometimes for mana as well) the ability activates every single time a creature is killed.
Edit: Maybe this'll help. I found some specific cases(with some help from Troy) where the bug always shows up. I'll use Propeller Mutant for simplicity.
>If Propeller was the last creature that was summoned/charged as mana, all cards in both players' mana and battle zones get its on-death ability until Propeller leaves the zone. >If you summon/charge another creature after Propeller, all cards get the new creature's on-death ability instead. If it doesn't have any on-death ability, then all creatures lose the previously activated ability(Propeller included). >If this new creature leaves the battle/mana zone before Propeller does, all cards revert back to having Propeller's ability. ...that's all I've found out so far. (And one additional variant where all creatures get Mighty Shouter's ability but killing those puts Mighty Shouter into mana, not the creature itself.)