Did not occur to me to have a save file on hand long after the fact, but here is a bug or merely an unforeseen if still legitimate outcome of a game feature:
A MegaScorpion hunt mission spawned, flied over to hunt them, and I see that they were replaced by Ratman Brigands.
Normally this is nothing unusual, missions occasionally feature a different enemy set than expected, most commonly the zombies.
But the two things that made this one funnily unusual is that they were a lot of them (AFAIK the game cannot re-adjust the numbers for the new enemy set, which can lead to some rather "interesting" scenarios) and that every single one of them had a MegaScorpion Sting/Tail in their inventories.
So now I'm imagining that a lot of angry wannabe rat ninjas were sloppily disguising themselves as scorps by tying the Stings on their backs, as they waited for the Piratez to arrive and to exact revenge on them for one Rodeo too many.