No, I don't know why Andrew Tate is turning into a catgirl either.

Despite consistent warnings from alchemists about the dangers of sharing custom health potions, the reality of adventuring often makes it unavoidable. When a companion is bleeding out, no one stops to weigh a lecture from some old brewer before pouring their own potion down his throat. An adventurer might take a swig to stabilise themselves before handing the dregs to their friends to finish. Having an alchemist in the party can even worsen matters, as cross-contamination is almost inevitable when brewing in the chaotic environment of a dungeon. Over prolonged usage, these alterations can become permanent.

The consequence is that, over a long quest, adventurers can begin to resemble one another, bodies blurring together, until the disparate band of races that set out return home resembling close family members, or even twins. Many great dynasties in history were even founded by the formalisation of a retired adventuring party (and their loot) into a single family.

Some parties even welcome the effect as the physical embodiment of the close bonds adventurers form.